Kryptonite's two best-known bike locks, one millimeter of shackle apart on paper and a whole security tier apart in practice. What each listing publishes, and which risk each one is actually built for.
Buy the Evolution Mini-7 if the bike is left in public where somebody might work on it, and the Keeper if it is left briefly, in daylight, in places you would describe as quiet. That is the whole decision, and it is not really about the one millimeter between a 13mm and a 12mm shackle. It is about which of the two carries an independent attack rating: the Evolution listing states Sold Secure Gold, and the Keeper listing states no independent rating at all.
Kryptonite publish their own 1-to-10 security scale across the range, and their own buying guidance is to match the rating to where and how long the bike is left. The Evolution sits high on that scale and the Keeper is the entry tier. Both are real locks; only one of them is built to be attacked.
If your problem is reach rather than resistance — you need to get the frame, both wheels and a fence post inside one lock — neither U-lock does it and the Keeper 712 chain does, at a rating its own listing publishes as 5 out of 10.
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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 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.
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.
Four feet of 7mm hardened chain in a sleeve. Chains are the answer when you need to secure the frame and both wheels to something fixed, and no U-lock is long enough to do that.
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 shackle, near the top of Kryptonite's consumer range
+Small shackle opening leaves no leverage space for a jack or bar
+Includes a 4ft cable so the front wheel is covered too
+High on Kryptonite's published security scale, which is a comparable number
What you give up
−The small U is genuinely hard to get around some racks and posts
−Heavy — you feel this in a jersey pocket or a small bag
−Roughly four times the price of the Parkview
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
Cable
4 ft
Locking
Key
Weight
Not published
Specifications read from the retailer listing on August 11, 2026. “Not published” means the listing does not state that figure — we do not estimate it.
#2Best for quiet, short stops
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
−Heavy — noticeably so on a bike you were choosing by weight
−The Keeper is Kryptonite's entry lock, not their highest security rating
−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
Cable
10mm x 4ft braided steel
Mounting bracket
Included
Security rating
Not published
Weight
Not published
Specifications read from the retailer listing on July 23, 2026. “Not published” means the listing does not state that figure — we do not estimate it.
#3Best for reach around awkward objects
Kryptonite Keeper 712 Chain Lock
Four feet of 7mm hardened chain in a sleeve. Chains are the answer when you need to secure the frame and both wheels to something fixed, and no U-lock is long enough to do that.
Who it is for: Locking a whole bike, wheels included, to a fixed object.
What is good
+4ft of chain reaches around frame, wheel and rack in one loop
+7mm hardened manganese steel links
+Fabric sleeve stops the chain marking the frame
+Kryptonite security rating published for honest comparison
What you give up
−Heavy — a chain this length is the heaviest option on this page
−7mm is at the lower end for a chain; bolt cutters are the known threat
−Awkward to carry on the bike without a bag or a rack
Skip this if. Skip this if you carry the lock in a jersey pocket. A 4ft chain is a bag or a rack purchase, and if neither exists, you will stop bringing it — which is worse than a lighter, weaker lock you actually use.
Published specifications for the Kryptonite Keeper 712 Chain Lock
Type
Chain lock
Length
4 ft
Link thickness
7mm hardened steel
Locking
Key
Weight
Not published
Specifications read from the retailer listing on August 11, 2026. “Not published” means the listing does not state that figure — we do not estimate it.
The three locks, from the listings
Read straight from the listings recorded in each product’s entry above, all three re-read on the date at the top of this page. The two rows that decide the purchase are the rating rows, and note that they are populated differently on each lock — which is itself the finding.
Evolution Mini-7
Keeper U-Lock
Keeper 712 chain
Shackle or link
13mm hardened steel shackle
12mm hardened steel shackle
7mm hardened steel links
Independent attack rating
Sold Secure Gold, stated on the listing
Not stated on the listing
Not stated on the listing
Manufacturer security rating
Not stated on the listing
Not stated on the listing
5 out of 10, stated on the listing
Reach
Mini U — deliberately small opening
4 x 8 in interior
4 ft / 120 cm of chain
Cable included
4 ft
4 ft
None — the chain is the reach
Locking mechanism
Double deadbolt, 3 keys
Key, 2 stainless steel keys
Key, 2 keys
Mount included
FlexFrame-U bracket
Frame mounting bracket
None
Weight
Not published
Not published
Not published
Why one millimeter is the wrong way to read this
13mm against 12mm looks like a rounding error, and if the shackle diameter were the only variable it nearly would be. It is not. A U-lock resists two different attacks, and the shackle diameter only answers one of them.
Cutting. Thicker hardened steel takes longer to cut, and that is where the millimeter helps a little.
Leverage. A bar, a jack or a scaffold pole pushed into the empty space inside the U and twisted. This is the attack that actually opens most locks, and it is beaten by geometry, not by diameter.
That is the real design argument for a mini U-lock. The Evolution Mini-7 has a deliberately small opening, so there is very little air inside the lock for a tool to get into. The Keeper publishes a 4 x 8 inch interior — roomier, easier to get around a rack and a wheel, and that extra room is also the space an attack needs. The Evolution also publishes a double deadbolt, meaning the shackle is held at both ends rather than one, so cutting one side does not release the lock.
What the Keeper is genuinely good for
It would be easy to write the Keeper off, and that would be wrong. It is a real U-lock with a hardened 12mm shackle, a 4-foot cable for the wheels and a frame bracket so the lock rides on the bike instead of in a bag — and a lock in a bag at home protects nothing.
The Keeper is the right buy when the honest answer to “where does the bike live?” is: indoors, mostly, and outside for twenty minutes at a time while you are inside a shop in daylight. Kryptonite’s own guidance is to match the lock to the exposure, and buying four times the lock you need has a cost you pay on every ride in weight you carry.
It is also the lock that comes with the thing people actually lose bikes to: the cable for the front wheel. Quick-release wheels come off in seconds, and a U-lock through the frame alone leaves them there to be taken.
When the Evolution is the only sensible answer
Locked up on a city street. Left at a station all day. Left outside overnight. Left anywhere you have seen a cut cable on the ground — that is somebody telling you what happens there. In those places the Evolution’s Gold rating and small shackle opening are the point, and the two costs are real: it is substantially heavier than the Keeper, and the small U is genuinely awkward to get around some racks and posts. Scout what you will be locking to before you buy a mini.
No lock is a guarantee. An angle grinder goes through any of these three, which is why the published ratings are expressed in resistance time rather than in yes or no. The useful goal is to be a slower target than the bike next to you, and to take the parts that unbolt with you. Our storage and security guide covers the rest of that: where the bike sleeps, what to photograph, and the serial number you will need if it goes.
The chain, and the problem it solves that U-locks cannot
Both U-locks are limited by their own shape. If the thing you want to lock to is a thick post, a wide railing or a lamppost, a U simply will not close around it, and an unlocked bike beside an immovable object is still an unlocked bike.
Four feet of 7mm chain goes around the frame, a wheel and most street furniture in one loop, and the sleeve stops it chewing the paint. Its own listing publishes the trade-off honestly as 5 out of 10: 7mm links are at the lower end for a chain, and bolt cutters are the known threat. It is also the heaviest option here and comes with no mount, so it is a rack or a bag purchase — and a lock too annoying to bring is worse than a lighter one you actually use. If your issue is awkward geometry rather than a thin chain, a folding lock is the other answer, and the full lock shortlist has one with live prices.
Which one for your parking
City streets, stations, anywhere overnight. Evolution Mini-7. The Gold rating is the reason; accept the weight and check the racks you use.
Suburban stops, workplaces, daylight, under an hour. Keeper U-Lock. Use the cable on the front wheel every time, not just when you remember.
Nothing a U-lock will fit around. Keeper 712 chain, and plan where it rides on the bike.
The bike lives indoors and never gets left in public. None of these yet. Spend it on lights and a floor pump, which you will use on every ride.
What we would buy
For a first bike that is ever left in public for more than a few minutes, the Evolution Mini-7. It is the only lock on this page whose listing carries an independent attack rating, and a lock is the one purchase on this site where the downside is losing the bike rather than being mildly disappointed.
For a bike that lives in a hallway and comes out for rides, the Keeper, carried on its bracket, cable through the front wheel. And if you are commuting daily, read bike commuting for beginners before you buy anything — where you park every day decides this question more than the specification does.
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
Is the Kryptonite Evolution better than the Keeper?+
For security, yes, and not by one millimeter of shackle. The Evolution Mini-7 listing states Sold Secure Gold and a double deadbolt, and its small shackle opening leaves little room for a leverage attack. The Keeper is Kryptonite's entry tier with no independent rating stated — a real lock for low-risk parking, not a city lock.
What is the difference between a Kryptonite Keeper and a Keeper 712?+
Shape, not family. The Keeper U-Lock is a 12mm shackle with a 4 x 8 inch interior and a 4-foot cable. The Keeper 712 is a 4-foot chain of 7mm hardened links with no cable, for locking to objects a U-lock cannot close around. Its listing publishes a manufacturer security rating of 5 out of 10.
Is a mini U-lock more secure than a bigger one?+
Usually, for the same shackle diameter, because the attack that opens most U-locks is leverage rather than cutting. Less empty space inside the U means less room to insert a bar or a jack. The cost is practical: a mini will not fit around some racks and posts, so check what you lock to before buying one.
What does Sold Secure Gold mean?+
Sold Secure is an independent body that attacks locks with tools for a fixed period and awards Bronze, Silver, Gold or Diamond by how long they resist. It is not the manufacturer's own number, which is why we treat it differently from Kryptonite's 1-10 scale.
Will any of these stop an angle grinder?+
No, and no consumer bike lock claims to. That is why ratings are expressed as resistance rather than prevention. The practical plan is to raise the time and noise cost above the bike beside yours, park where there are people, and take the quick-release parts with you.
How much do these Kryptonite locks weigh?+
None of the three listings publishes a weight, so we do not publish one. What the listings do establish is the order: the 4-foot chain is the heaviest, the 13mm Evolution next, and the Keeper U-lock the lightest of the three.
Do I need the cable as well as the lock?+
If your wheels are quick-release, yes. A U-lock through the frame and rear wheel leaves the front wheel held by a lever anyone can open. Both U-locks here include a 4-foot cable for exactly that; the chain is long enough to loop a wheel instead.
Sources
Specifications come from the manufacturer or the retailer listing, dated. Where a figure is not published, we say so rather than estimating it.
