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What is a Dumbbell Type Lock


There are so many different types and styles of padlock available today it can be difficult to identify the best for a specific need. One of the most popular types available from our store is the Roundlock RL21 Dumbbell type of padlock. In this post we look more closely at this popular padlock and how its typically used.

The first thing to clear up regarding dumbbell type padlocks is that they are not locks for dumbbell weights, sometimes called weight bar collars, dumbbell collars or barbell collars. These refer to devices used in weightlifting and training.

dumbbell rl21 roundlock
RL21 Roundlock - Dumbbell Type Lock

Dumbbell type locks derive their descriptive name from their appearance. They simply look like miniature dumbbells.

Roundlock or Dumbbell Type Lock

The popular dumbbell type padlock available from our store is also known as the RL21 Roundlock. Its a compact, lightweight, high security padlock that’s recognised for being enormously strong and almost indestructible.

Its a two part locking mechanism wherein the ‘male’ section detaches completely enabling the shaft to be passed through a security chain and reinserted into the ‘female’ (socket) section and securely locked in place.

dumbbell lock with security chain
Dumbbell Type Lock with High Security Chain

The RL21 dumbbell type padlock is designed to be used with security chains from 13mm up to 19mm. But it must be noted that an alternative special socket (RL21A) is needed for use with a 19mm high security chain. This special female section of the lock has a chamfered profile that enables the lock to be used with the larger 19mm high security chain link dimensions.

If you are uncertain whether an RL21 dumbbell type padlock will work with your security chain, give us a call on 01273 475500 - we are always happy to help!

Dumbbell Type Lock Applications

Since the RL21 dumbbell type lock is highly compact and very lightweight its very popular in applications where these features are important. Motorcyclists appreciate these attributes along with the fact that Bennetts have rigorously tested and evaluated the lock, acknowledging that it is almost indestructible. This is what they had to say after subjecting this lock to some serious and nasty attacks.

...the RoundLock is an excellent piece of kit, fitting snugly against the edges of the chain`s links, making it very difficult to attack.
When attacked with a sledgehammer, the lock merely deformed (the shape of the lock itself makes it very difficult to hit squarely).
It`s inaccessible with bolt croppers, and is so thick that an angle grinder attack causes little damage – in fact the chain is the easier option for a crook to attack ...and that is also a very tough cookie to crack!

As noted, the RL21 Roundlock can be used with 13mm, 16mm and 19mm high security chains. So these locks are widely used to secure high value vehicles and property including: quad bikes, all terrain vehicles, bicycles, scooters, plant and machinery, agricultural equipment, barns, sheds, boats, trailers - and much more.

Each RL21 dumbbell lock is supplied with three keys and locks can be keyed alike to other RL21 locks which is great for people using one lock for their security chain and another as a motorbike disc lock.

Dumbbell Motorcycle Disc Lock

The fact that this compact and lightweight (0.53kg) padlock can be used as a motorcycle disc lock is one of the key reasons for its popularity with motorcyclists.

Motorbike disc locks operate by effectively locking a motorcycle’s brake disc in place, preventing the wheel from being rotated. The shaft of the dumbbell lock is simply passed through an existing aperture in the motorbike’s brake disc, locking into the female section on the other side.

When purchasing an RL21 Roundlock to be used as a motorbike disc lock its essential to verify the dimensions of the available apertures on the motorbike brake disk. The shaft or male section of the RL21 has a robust diameter of 21mm, so the available holes must be big enough to accomodate this. The space between the male and female sections of the RL21, when locked, is 15mm - which is large enough to accommodate most motorbike brake discs. 

dumbbell disc lock dimensions
Dumbbell Disc Lock Dimensions

When ordering an RL21 Dumbbell type lock to be used as a motorbike disc lock always check the dimensions of the holes in your brake disc.

dumbbell disc lock
Dumbbell Disc Lock in Use

Sold Secure Motorcycle Gold Accreditation

Importantly, the RL21 Dumbbell type lock has achieved Sold Secure Motorcycle Gold accreditation. This means the lock has been subjected to all manner of attacks by specialist assessors in the Sold Secure labs. They use many of the tools and techniques commonly employed by criminals to determine the level of security offered by the lock and the RL21 has been awarded what is effectively a gold star.

Customer Reviews

Our RL21 Dumbbell type locks are extremely popular and we continuously receive outstanding reviews like these.

Great product and great service. Fast delivery and exceptional packaging.

Andrea Grange

Good solid bit of kit, looks very good quality and delivered in record time during Covid-19 lockdown. What more can you ask

David Rowles

Good quality


RoundLockSold Secure Motorcycle Gold Dumbbell Type Lock - Very pleased with the lock as it will satisfy any insurance company that questions my level of security. It works with my Torq Ground Anchor and 16mm Protector Gold Secure Chain - Will protect my New Insurance Replacement Bike.

Graham Hemmings

Very sturdy lock, looks well made. Very happy with my purchase.

Ken Clarke

If you have any questions about motorbike security or using our RL21 Dumbbell type locks remember that we are here to help. Give us a call on 01273 475500 and we’ll provide you with free, expert advice.

This message was added on Thursday 7th October 2021

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