Replacement chain tensioner idlers and fittings

The chain tensioner on the Brompton keeps the chain taut, both when riding and when folded (to stop it falling off of the front chain ring)

The chain passes over the two jockey / idler wheels on the chain tensioner - and over time (that time depends upon riding conditions / style and especially how clean the chain is) they can wear - causing the chain to start slipping (the same applies to the rear sprockets)

This is a replacement pair of jockey wheels for the chain tensioner (sometimes called a derailleur even though on this model it is not - it just keeps the chain tension correct when riding and folded)

For use on single, three and five speed Bromptons (i.e. for Bromptons with a standard - non-derailleur - chain tensioner)

A new set (pair) of Jockey / idler wheels for the chain tensioner