Illustrative imageSeatylock · D-lock
Seatylock Mason 140
A Sold Secure Diamond D-lock at about 0.97kg.
Diamond (ordinary bikes)
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See on AmazonThe lightest published Diamond D-lock in this set for daily bag carry — after you have measured the short 140 × 85 mm locking area.
The Mason 140 is Sold Secure Pedal Cycle Diamond at about 0.97kg, which suits ordinary-bike Diamond when carry weight is the limit. The locking area is a compact 140 × 85 mm, so measure your stand first. The mount is sold separately, and you should confirm any e-bike grade on Sold Secure.
Verdict
The Mason 140 is Sold Secure Pedal Cycle Diamond on the Sold Secure record. Manufacturer and retailer sheets put the weight at about 0.97kg and the locking area at 140 × 85 mm. That’s meaningfully lighter than the Diamond D-locks already in this set. The shackle is a triangular profile rather than a round bar, so millimetre comparisons with other locks aren’t direct. The frame mount is sold separately. Powered Cycle (e-bike) Diamond isn’t listed on that Sold Secure product page — confirm on Sold Secure if your policy names the e-bike grade. We’d skip it if Gold is enough, if you need a longer shackle, or if you want a clip in the box.
See on Amazon- Weight
- 0.97kg
- Sold Secure
- Diamond
- Locking area
- 140 × 85 mm
Who this suits
- Ordinary bikes where the policy names Pedal Cycle Diamond and carry weight is the main limit
- Weekday bag carry when about 0.97kg is realistic and 1.4–1.93kg is not
- Tight stands you’ve already measured against 140 × 85 mm
Less suitable if
- Gold meets the policy — the Evolution Mini-7 is the clearer Gold commute kit with a mount and cable
- You need a longer shackle or more internal room than 140 × 85 mm
- You want a frame mount in the box
- The policy names Powered Cycle Diamond and you haven’t confirmed this model on Sold Secure
Among the Diamond D-locks reviewed here, the next lightest clipped option is the Pitbull STD at 1.44kg, and the bag-carry X1 and D1000 sit at 1.7kg and 1.93kg. A published weight of about 0.97kg is the reason this lock exists on Lock Desk: it’s for riders whose policy names Diamond and who won’t take 1.4–1.93kg every day. A lighter lock you take still beats a heavier Diamond lock left at home.
Weight under 1kg, and what that means for a commute
That weight gap is the commute case. If about 0.97kg is a lock you’ll keep putting in a bag, Pedal Cycle Diamond becomes usable on weekday stands. If you already leave 1.7kg at home, stepping up a grade on paper won’t protect your bike at the station.
The short 140 × 85 mm locking area
The locking area is compact: 140 × 85 mm on manufacturer and retailer sheets. That’s short and narrow next to the Pitbull STD (115 × 230 mm) and the X1 (101 × 197 mm). It’s closer in spirit to a Mini. Measure your stand plus the frame tube before you buy. Fat tyres, cargo frames, and many UK lamp-posts won’t close. If a compact lock already fails on your rack, look at the Pitbull LS, the ABUS 540, or a longer Mason size rather than guessing from a photo.
Pedal Cycle Diamond — check e-bike grades separately
Sold Secure lists Pedal Cycle Diamond for the Mason U Lock 140. The public product page doesn’t show a Powered Cycle grade. Category labels for e-bike security on that site aren’t the same as a Powered Cycle Diamond row. If you ride an e-bike and the policy names the powered grade, confirm the exact model on Sold Secure and on the insurer’s list before you treat this as an e-bike Diamond lock. The X1, D1000 and DX1000 are Diamond for both ordinary bikes and e-bikes.
Mount sold separately, and triangular shackle numbers
Amazon’s listing for this size states that the mounting bracket is sold separately. Budget for Seatylock’s bracket, or carry the lock in a bag. The shackle uses a patented triangular crossbar profile. Retailer sheets often quote about 13.7 mm; that isn’t a round-bar figure you can line up cleanly with the 14 mm Pitbull or the 32 mm Hiplok D1000. Rely on the Sold Secure grade and whether the lock closes, not on a millimetre contest. Maker lines about uncuttable locks or grinders are advertising. Diamond is a tougher Sold Secure test than Gold. It isn’t a promise that a battery grinder will fail.
When to choose this lock or another
Choose the Mason 140 when Pedal Cycle Diamond matches the policy, 140 × 85 mm will close, and carry weight is the limiting factor. Choose the Pitbull STD if you need Diamond with a clip in the box and more room inside the shackle. Choose the X1 if you need Diamond for ordinary bikes and e-bikes with a larger locking area at about 1.7kg. Choose the D1000 only after you’ve measured its 92 × 155 mm hole. Choose the Evolution Mini-7 if Gold is enough and you want a mount and cable in one kit.
What works well
- Sold Secure Pedal Cycle Diamond on the Sold Secure record
- Published weight about 0.97kg — lighter than the other Diamond D-locks on this site
- Compact form many people will actually take every day
- Three keys and a key-duplication card listed on the Amazon kit
What to watch for
- 140 × 85 mm is small; many UK stands won’t close — measure first
- Frame mount sold separately
- No Powered Cycle grade on the Sold Secure product page
- Triangular shackle — published millimetre figures aren’t directly comparable to round bars
One thing we’d change
Include a frame mount as standard, and publish the ordinary-bike grade next to a clear e-bike line so buyers aren’t left guessing from category labels.
The numbers
The weights, grades and sizes below come from the maker and from Sold Secure. If a figure’s missing, we’d rather leave the cell blank than guess.
| Grade | |
|---|---|
| Sold Secure (ordinary bikes) | Diamond |
| Maker says it resists grinders | No |
| Size and weight | |
| Type | D-lock |
| Locking area | 140 × 85 mm |
| Weight | 0.97kg |
| In the box | |
| Frame mount | No |
| Cable included | No |
| Keys | 3 |
Other options
Another option
OnGuard Pitbull STD 8003
You need Pedal Cycle Diamond with a frame mount in the box and more room inside the shackle (115 × 230 mm at 1.44kg).
See on AmazonAlso worth a look
Litelok X1
You need Diamond for ordinary bikes and e-bikes, with a larger locking area, and you’ll still carry about 1.7kg.
Not currently available on Amazon UKCommon questions
Is the Seatylock Mason 140 Sold Secure Diamond?
Yes for ordinary bikes — Pedal Cycle Diamond on the Sold Secure Mason U Lock 140 page. Powered Cycle (e-bike) Diamond wasn’t listed on that page. Confirm the marking on the lock you buy, and your insurer’s list.
Is it really under 1kg?
The maker and retailers put this 140 mm size at about 0.97kg, so that’s the figure we’d plan on. To be fair to you, we haven’t weighed one ourselves.
Will it fit my bike stand?
Only after you measure. The locking area is 140 × 85 mm. That’s short. If a Mini already fails on your stand, this one may fail too. Look at the Pitbull LS or the ABUS 540 for longer shackles.
Does it come with a frame mount?
No. The Amazon listing for this size says the mounting bracket is sold separately. Plan on a bag or buying Seatylock’s bracket.
Mason 140 or Litelok X1?
The Mason is lighter (about 0.97kg) with a smaller locking area, and Pedal Cycle Diamond on our Sold Secure check. The X1 is 1.7kg with 101 × 197 mm and Diamond for ordinary bikes and e-bikes. Choose on e-bike grade, fit, and whether you’ll carry 1.7kg.
Mason 140 or Hiplok D1000?
Both are compact Diamond options. The D1000 is 1.93kg with a 92 × 155 mm hole and is sold as anti-grinder; it’s also Diamond for e-bikes. The Mason is lighter. Measure both holes before you pick on marketing alone. Full D1000 write-up: Hiplok D1000.
If you haven’t measured your stand yet, start with how to choose a bike lock. You can compare the shortlist on best bike locks UK, or read D-lock vs chain. For the differences between lock types, see bike lock types explained, and for sizing, see shackle size and lock security. For how the research is put together, see how we research.
Prices and stock on Amazon can change, so it’s worth a check on the day you click through.
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