Roundlock and Protector chain compatibility

Updated on Oct 13, 2026

The Roundlock works with our Protector 13mm and 16mm chains. For a 19mm or 22mm Protector chain you need the RL21A socket.

Which socket do I need?

Protector chain	Roundlock option
13mm	Standard RL21 socket
16mm	Standard RL21 socket
19mm	RL21A socket required
22mm	RL21A socket required

How do I lock the chain ends together?

Pass one end-link through the other, then fit the Roundlock through the part of the link that protrudes. The lock closes around one link, rather than both end-links together.

Why will my Roundlock not close on a 16mm chain?

Position the lock on the straight part of the protruding link, away from the curved end and the weld. These wider areas can prevent the socket from seating fully. Check that the socket is fully engaged before removing the key; do not force it into place.

Can I use the RL21A with a 22mm chain?

Chain gauge alone does not establish compatibility. A 22mm chain from another manufacturer can have a different link shape and internal clearance.

Was it helpful?

Yes

Neutral

1000s of customers trust Pragmasis

Established in 2003, we've built our business on quality, reliability and customer service.

James T

Great products

Thanks for some great products. Your kit protected my bikes perfectly during a burglary a few years ago and it’s still going (extremely) strong.

Ben R

Still going strong

I bought from you once and only needed to buy once in 2016, but suffice to say that the 19mm bespoke length chain, and ground anchor installed according to Pragmasis instructions are still going strong, keeping my bike safe just off the street in Brixton, London.

Mr B

Wholly impressed

I would like to say I am wholly impressed with the ground anchors, chains and padlocks that I have purchased over the past few years and will always recommend you when the opportunity arises.

C Rowe

Torc Ground Anchor

Excellent quality piece of kit. Our second anchor to date. Exceptional service. Nice to see a British company up there supplying quality goods and customer service

Steve

Top class service

This is a serious chain! I certainly feel more comfortable that my bikes are well secured. Very pleased with the service too. I phoned then placed an online order and my chain arrived the next day. Excellent product and 1st class service. Thank you!