Two mini U-locks from the same brand, three tenths of a millimeter of shackle apart, in the same shape, at clearly different prices. One of them carries an independent attack grade. That is the whole decision.
Buy the KryptoLok Mini-7 for commuting, campus and suburban racks. Buy the Evolution Mini-7 if the bike is left locked outdoors in a city, or if you want a lock that has been independently attack-tested. These two are closer than their prices suggest: both are small Us with the same published 3.25 by 7 inch opening, both include a 4 ft cable and the same frame bracket, and the shackles are 12.7mm and 13mm.
So the millimeter is not the difference. The difference is a certification. The Evolution Mini-7 listing publishes a Sold Secure Gold rating — an independent testing body’s grade, not a marketing scale. The KryptoLok Mini-7 listing publishes no grade at all, even though the full-size KryptoLok Standard listing publishes Sold Secure Silver.
That is the honest version of this comparison, and it cuts both ways. An ungraded lock is not a bad lock — it is the same shackle diameter, the same double deadbolt and the same cylinder as a graded one, at a clearly lower price. But if you want the grade in writing, there is only one of these two that gives it to you, and no amount of reading the shackle number changes that.
How this is funded: we earn a commission if you buy through our links, at no extra cost to you. It never changes which bike we recommend, and we will tell you plainly when we would skip one. Full disclosure.
Quick picks
Ranked on published specs, what the listing does and does not tell you, and who each one actually suits. Select a row to jump to the full write-up. We have not ridden these — here is exactly what we do instead.
#
Bike or gear
Best for
Price
1
Kryptonite KryptoLok Mini-7
The same small-U shape and the same published 3.25 by 7 inch opening as the Evolution Mini-7, with a 12.7mm shackle instead of 13mm and a clearly lower price. What it does not have is the Evolution's independent Sold Secure grade.
The lock to buy if the bike is genuinely at risk. A 13mm shackle in a deliberately small U, because the less air inside the lock, the less room a thief has to get a tool in — that is the whole design argument for a mini.
A 12mm hardened shackle plus a 4-foot cable, which lets you lock the frame and both wheels to something solid. Kryptonite is the name thieves recognize, and that matters more than the specification.
The same small-U shape and the same published 3.25 by 7 inch opening as the Evolution Mini-7, with a 12.7mm shackle instead of 13mm and a clearly lower price. What it does not have is the Evolution's independent Sold Secure grade.
Who it is for: A first serious lock, for a bike left in public for an hour or two.
What is good
+12.7mm hardened steel shackle, within three tenths of a millimeter of the Evolution's
+Same published 3.25 in x 7 in opening as the Evolution, so it fits the same racks
+Lighter than the Evolution on the published figures — 3.25 lb against 3.55 lb
+Includes a 10mm x 4 ft looped cable, so the front wheel is covered without a second purchase
+Three keys and the FlexFrame-U frame bracket in the box
What you give up
−This listing publishes NO independent attack grade, while the Evolution Mini-7 listing publishes Sold Secure Gold and the full-size KryptoLok Standard listing publishes Sold Secure Silver — on paper this lock is ungraded
−A 3.25 x 7 in opening is genuinely tight around thick posts and some rack designs
−Noticeably more expensive than the Keeper for a difference most short-stop parking will never test
−The included cable deters an opportunist with hand tools and nothing more
Skip this if. Skip this if the bike is only ever locked for ten minutes outside a cafe in a quiet place. The Keeper is lighter, cheaper and enough for that, and the weight you do not carry is weight you do not resent.
Published specifications for the Kryptonite KryptoLok Mini-7
Type
Mini U-lock with cable
Shackle
12.7mm hardened steel
Interior opening
3.25 in x 7 in
Cable
10mm x 4 ft looped steel
Locking
Key (3 included)
Weight
3.25 lb (published)
Independent rating
Not published
Specifications read from the retailer listing on October 24, 2026. “Not published” means the listing does not state that figure — we do not estimate it.
#2Best for high-risk parking
Kryptonite Evolution Mini-7
The lock to buy if the bike is genuinely at risk. A 13mm shackle in a deliberately small U, because the less air inside the lock, the less room a thief has to get a tool in — that is the whole design argument for a mini.
Who it is for: City parking, or anywhere the bike is left for hours.
What is good
+13mm hardened Max-Performance shackle, near the top of Kryptonite's consumer range
+Sold Secure Gold certified on the listing — an independent attack grade, not a brand scale
+Small 3.25 in x 7 in opening leaves no leverage space for a jack or bar
+Includes a 4 ft double-loop cable so the front wheel is covered too
+Three keys plus the Kryptonite Key Safe program, and the FlexFrame-U bracket in the box
What you give up
−The small U is genuinely hard to get around some racks and posts
−3.55 lb published — you feel this in a jersey pocket or a small bag
−The most expensive lock on our shortlist by a clear margin
Skip this if. Skip this if you mostly stop for ten minutes at a time in quiet places. The weight and the awkward small shackle are a daily cost you pay for a risk you are not carrying.
Published specifications for the Kryptonite Evolution Mini-7
Type
Mini U-lock with cable
Shackle
13mm hardened steel
Interior opening
3.25 in x 7 in
Cable
4 ft double-loop
Locking
Key (3 included)
Weight
3.55 lb (published)
Independent rating
Sold Secure Gold
Specifications read from the retailer listing on October 24, 2026. “Not published” means the listing does not state that figure — we do not estimate it.
#3Best cheap lock that is still a lock
Kryptonite Keeper U-Lock with Cable
A 12mm hardened shackle plus a 4-foot cable, which lets you lock the frame and both wheels to something solid. Kryptonite is the name thieves recognize, and that matters more than the specification.
Who it is for: Leaving the bike outside anywhere, ever.
What is good
+12mm hardened steel shackle — the published figure, which most locks hide
+Included 10mm x 4ft cable secures both wheels, not just the frame
+Mounting bracket so the lock rides on the bike, not in a bag
+Kryptonite's reputation is a deterrent in itself
What you give up
−2.40 lb published — noticeably heavy on a bike you were choosing by weight
−The Keeper is Kryptonite's entry lock, and its listing publishes no independent attack grade at all
−A 4 in x 8 in opening leaves more air inside the U than a mini does, which is leverage room
−The cable is a deterrent against opportunists, not a serious barrier
Skip this if. Skip this if the bike lives indoors and never gets left in public. It is a lot of weight to carry for a risk you are not taking, and the money is better spent on a floor pump and lights.
Published specifications for the Kryptonite Keeper U-Lock with Cable
Shackle
12mm hardened steel
Interior opening
4 in x 8 in
Cable
10mm x 4ft looped steel
Mounting bracket
Included
Locking
Key (2 included)
Independent rating
Not published
Weight
2.40 lb (published)
Specifications read from the retailer listing on October 24, 2026. “Not published” means the listing does not state that figure — we do not estimate it.
The three locks, from the listings
Every value below was read from the Amazon listing recorded in each product’s entry above, on the date that entry records. Four rows decide this page: the grade, the opening size, the weight and the price.
KryptoLok Mini-7
Evolution Mini-7
Keeper U-Lock
Shackle
12.7mm hardened steel
13mm hardened Max-Performance steel
12mm hardened steel
Independent grade on the listing
None published
Sold Secure Gold
None published
Published interior opening
3.25 in x 7 in
3.25 in x 7 in
4 in x 8 in
Published weight
3.25 lb
3.55 lb
2.40 lb
Cable included
10mm x 4 ft looped
4 ft double-loop
10mm x 4 ft looped
Keys in the box
3
3
2
Locking mechanism
Double deadbolt, disc-style cylinder
Double deadbolt, disc-style cylinder
Disc-style cylinder; deadbolt type not published
Frame bracket
FlexFrame-U included
FlexFrame-U included
Included
Price band
Mid
Premium
Mid, cheapest of the three
What a Sold Secure grade actually is
Sold Secure is an independent body that attack-tests locks with the tools thieves actually use and grades them Bronze, Silver, Gold or Diamond. That is structurally different from a manufacturer’s own security scale: the brand’s scale lets you compare its own products to each other, while a Sold Secure grade lets you compare locks from different brands on the same basis.
It is also the only number in this category that is not written by the seller. Kryptonite publish their own 1-to-10 scale alongside guidance on matching a rating to where and how long a bike is left, and that guidance is genuinely useful — but it is theirs. When a listing carries Gold, somebody outside the company put a tool to it.
What a grade does not tell you is how long the lock survives a battery angle grinder, because almost nothing in this price range survives one. Grades are a comparison between locks, not a promise about outcomes.
Why the shackle number is the wrong thing to compare
A U-lock fails in one of four ways: the shackle is cut, the shackle is levered apart, the cylinder is picked or drilled, or — most often — nothing is attacked at all, because the bike was locked by the front wheel and the rest of it was carried away. Three tenths of a millimeter of steel changes the first of those slightly and the other three not at all.
Both of these locks use a double deadbolt, which means the shackle locks on both sides of the crossbar instead of one — that is the feature that resists twisting and pulling, and it is identical on both. Both use a disc-style cylinder their listings describe as pick and drill resistant. And both are small Us with the same published opening, which is the real security feature: the less open air inside the lock, the less room there is to insert a bar or a jack and lever against the shackle. The Keeper’s 4 by 8 inch opening is roomier, and that roominess is leverage space.
The research on theft points the same way. The ASU Center for Problem-Oriented Policing’s review of bicycle theft found that most bikes are stolen at or near home, and that of 8,500 observed locking events in London only about a fifth used a secure method. Technique is doing more work than the spec sheet.
What the Evolution buys you
The grade, and the position in Kryptonite’s range that goes with it. Sold Secure Gold on a 13mm Max-Performance shackle is the strongest combination on this page, and some insurers and some workplace bike cages ask for a graded lock by name — a requirement no amount of equivalent engineering satisfies if the paperwork is missing.
The orange Kryptonite shell is also a recognizable object, and a thief choosing between bikes on a rack is doing exactly the triage that reputation is for.
It costs the most of the three by a clear margin, and it is the heaviest at a published 3.55 lb, carried on your frame or your back every ride. Those are real costs you pay on every single trip for a benefit you may need on none of them. That is the trade, and it is a genuine one rather than a reason not to buy it.
What the KryptoLok buys you
Nearly all of the Evolution’s hardware for clearly less money, in the same shape. Same published 3.25 by 7 inch opening, so it fits exactly the same racks. Same double deadbolt, same cylinder description, same three keys, same FlexFrame-U bracket, and a 10mm by 4 ft looped cable in the box. It is also lighter on the published figures — 3.25 lb against 3.55 lb.
Its weakness is the one thing it does not have, and we will not paper over it: no independent grade on the listing. If you are the sort of buyer who wants the tested number, this is not the lock, and the price saving is not an argument against the grade — it is the price of not having it.
For a bike parked where bikes are not routinely stolen, that is a reasonable trade. For a bike parked where they are, it is not, and the honest advice is to spend the difference rather than talk yourself out of it.
And the cheap option, honestly
The Keeperis Kryptonite’s entry lock: a 12mm shackle, a 4 in by 8 in opening, a published 2.40 lb and the same style of 4 ft cable, at the lowest price of the three. For a bike that lives indoors and gets locked for twenty minutes outside a coffee shop in a quiet place, it is enough — and it is more than a pound lighter than the Evolution, which is weight you do not carry on every ride.
For a commuter rack, a campus, a transit station or anywhere a bike sits for hours, it is not enough, and the reason is leverage rather than steel: the bigger opening leaves more air inside the U. The full lock shortlist, including chains and folding locks for the racks a mini will not reach around, is on our best bike locks page.
Which one for the way you actually park
Bike lives indoors, locked outside for short stops in quiet places. Keeper. Spend the difference on lights.
Commuting, campus, suburban racks, an hour or two at a time. KryptoLok Mini-7. Same shape and opening as the Evolution, less money.
City parking, street racks, all day, or an expensive bike. Evolution Mini-7, plus the cable for the wheels.
An insurer, a landlord or a bike cage asks for a graded lock. Evolution Mini-7. It is the only one of the three whose listing publishes a Sold Secure grade.
Your rack or post is too thick for a mini U. Neither mini. A folding lock or a chain reaches around things a mini cannot, and both are on the lock shortlist.
What we would buy
The KryptoLok Mini-7, for most readers of this site. It gives you the Evolution’s shape, its opening dimensions, its mechanism description and its cable for less money, and the saving is better spent on lights or a floor pump than on a grade you are not going to be asked for.
If the bike is expensive, if it lives outside, or if anybody is going to ask you which rating your lock carries, buy the Evolution and stop optimizing. And whichever you buy, photograph the bike and write down the serial number first: our storage and security guide covers why recovered bikes so often are not returned, and it is a proof-of-ownership problem rather than a locking one.
We have not ridden these bikes. Every site in this category says it tested twenty of them. We have not tested any, and we say so. What we did instead: read the manufacturer listings and manuals, compiled the published specs, worked out the real out-the-door cost, and checked live availability and price. Here is exactly how that works.
Questions people actually ask
What is the difference between the Kryptonite Evolution and the KryptoLok?+
Price and certification, mostly. The Evolution Mini-7 uses a 13mm Max-Performance shackle and its listing publishes a Sold Secure Gold grade; the KryptoLok Mini-7 uses a 12.7mm shackle and publishes no grade. Both are small Us with the same published 3.25 by 7 inch opening, the same double deadbolt, a 4 ft cable and a FlexFrame-U bracket.
Is the Kryptonite Evolution worth the extra money over the KryptoLok?+
If the bike is locked outdoors in a city for hours, or if an insurer or bike cage asks for a graded lock, yes — the Sold Secure Gold rating is the thing you are buying. For commuting, campus and suburban racks, the KryptoLok Mini-7 has the same shape and opening for clearly less money.
Is a 13mm shackle much stronger than a 12.7mm one?+
Not in a way you would notice. Three tenths of a millimeter is a rounding difference against bolt cutters and against an angle grinder alike. What genuinely changes a U-lock's resistance is the size of the opening, the double deadbolt, the cylinder, and how you thread it through the bike and the rack.
Is the KryptoLok Sold Secure rated?+
The KryptoLok Mini-7 listing we read publishes no Sold Secure grade. The full-size KryptoLok Standard listing publishes Sold Secure Silver, and the Evolution Mini-7 publishes Sold Secure Gold. Grades belong to a specific model and size rather than to a product name, so read the exact listing you are buying from.
Will a mini U-lock fit my bike rack?+
Both minis here publish a 3.25 by 7 inch interior opening, which is enough for a standard rack hoop plus a frame tube and often not enough for a thick post or a wide rack. Measure what you lock to before you buy — a mini U you cannot close around your rack is the most common way this purchase goes wrong.
Do I need the cable that comes with these locks?+
It is useful and it is not a serious barrier. Use it to catch the front wheel once the frame and the rear wheel are inside the U. A thief with cable cutters goes through it quickly, so never let the cable be the only thing securing a wheel you would mind losing.
How heavy are these locks?+
On the published figures: 2.40 lb for the Keeper, 3.25 lb for the KryptoLok Mini-7 and 3.55 lb for the Evolution Mini-7. All three are heavy enough that you will want the included frame bracket rather than a jersey pocket.
Sources
Specifications come from the manufacturer or the retailer listing, dated. Where a figure is not published, we say so rather than estimating it.
Kryptonite — Choosing your bike lock — Manufacturer guidance on matching lock rating to where and how long a bike is left (accessed August 11, 2026)
ASU Center for Problem-Oriented Policing — Bicycle Theft (Guide #52) — Research review finding most bikes are stolen at or near home, that only about 20% of 8,500 observed locking events in London used secure methods, and that the proof-of-ownership gap is why recovered bikes are not returned (accessed August 13, 2026)
