Seatylock Mason U-lock Review

Gear Recommendation: The Seatylock Mason U-lock is a Sold Secure gold lock that gives you a lot of lock and security at a good price point and weight. Buy it directly from Seatylock with free shipping. It also comes in a larger size than the one I reviewed.

I’m a big fan of high security U-locks to keep your bike safe. I’ve written about specific traits that should be in any u-lock you buy, and when I saw the Mason specs it looked like it hit all those requirements and then some. When Seatylock offered to send me one to review, I was excited to check it out.

The Mason Ulock comes in 2 sizes: the mini version is the 140 and the regular size one is 180. The number refers to the length in mm. I have the mini version and prefer it so I can lock my wheels separately, but if you want extra space or want to get a wheel and frame inside the u-lock, check out the longer version.

First off, Seatylock touts the Mason as the lightest sold secure gold lock on the market, which is true. If you believe in those ratings, this is a big plus. I personally don’t know enough about how they test these locks to make that a deciding factor, so that’s just the icing on the cake.

Why This Lock Will Keep Your Bike Safe

The Seatylock Mason has all the important traits of a quality ulock:

  • Double locking shackle of hardened steel: this means a thief would have to cut the lock twice to remove it. What a pain for them!
  • 17mm length on each side of the triangle: That’s a lot of mm to cut through, beat only by the heavy NYC Fahgettaboutit at 18mm. Not completely comparable since the Mason is a triangle and most other locks are cylinders, but it’s thick enough to resist bolt cutters, which is what you want.
  • Good construction that prevents other simple attacks. This is a quality lock that should resist simple stuff like drilling and freezing. Unsurprising considering its sold secure gold rating.
  • If you have the mini 85/140 version, it will be more difficult for a thief to fit something inside the lock to crank it open.
seatylock mason double locking shackle
Note the double locking shackle and the triangular bar.

What I Like about the Seatylock Mason U-lock

It’s these cool traits that set apart the Seatylock Mason as a great lock that’s fun and easy to use. Convenience is key, and this is one convenient lock.

  • Spring loaded locking mechanism. When you unlock the Mason Ulock, the lock doesn’t simply fall apart. It’s unlocked, but the locking mechanism is still engaged with a spring. You have to pull it apart to actually take it off (easy to see in my video). At first I thought this was annoying, but then I realized there are many instances when the lock is falling out of my other ulocks and I have to hold it in because I’m not ready to remove it yet. This solves that problem, and it’s not difficult to remove when you really want it off.
  • It’s quiet! When you shake the lock around it makes less noise than some other locks I have. This is a cool plus, but I did notice it sometimes made more noise depending on how I carried it. When I put it on the mounting bracket it made a lot of noise on bumpy roads, but when I put it in my basket it was super quiet.
  • Unnoticeable weather cover. The weather cover is spring loaded and works without you even noticing it’s there. If you read my other ulock post, you know I really don’t like invasive weather covers that I have to think about, so this is pretty snazzy.
  • Nice big key. It’s big and easy to hold. That’s all.
seatylock mason key and weather cover
You can see the key and (internal) weather cover here. Who’s up for the challenge to 3D print my key?

What I don’t Like

I honestly couldn’t find much bad about this lock. There are a few things that could be annoying depending on what you’re looking for, but in general they can also be seen as good traits.

  • The spring loaded locking mechanism takes some getting used to, especially if you’ve been using other ulocks. This depends on your preference. It’s easy to see this in my video review of the Mason.
  • It can be loud when used on the mounting bracket. Ironic that this is both the quietest and the loudest lock I’ve used. As I carry it in more ways I will update this post with my findings on noise.
  • If you have the mini 85/140 version, it can be more difficult to fit on a crowded bike rack, but I have tips for using a small u-lock that makes it easy!

Mounting the Lock on your Bike

A note on carrying your ulock, since you need a place to put it while riding your bike! If you don’t want to carry it in a bag or back pocket, you’ll need some extra hardware to mount it.

The Seatylock Mason doesn’t come with any mounting hardware, but you can buy it separately. You can’t use the standard kryptonite mounting hardware that I use for my Abus Ulock either since the Mason has a special triangular shape.


seatylock mason ulock on a road bike locked up
It says Pentagon Mason on the front, but don’t get it confused with the other lock they make with a Pentagon shape. This one has a triangular bar.

This Seatylock Mason Ulock is one of my new favorite locks, and I’m looking forward to using it more and posting any updates on long-term usage. Let me know in the comments your thoughts on this lock if you have it.

Happy biking!

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