Chain Tensioner for Brompton Derailleur Rear Pulley (2 speed or 6 speed)

This chain tensioner is for Brompton folding bikes with 2 speed, 6 speed SRAM or 6 speed Sturmey Archer / BWR (Brompton Wide Ratio) gears. This can be identified by the fact it has 2 identical looking black jockey wheels where the chain sits in a groove in the jockey wheel This works as a chain tensioner (keeping the chain tight when riding and folded) and as part of the Brompton designed derailleur mechanism - by having juckey wheels which can move from side to side to allow the chain to move between the two rear sprockets To make your chain tensioner last as longer - keep your chain clean and not over lubricated