Lightweight sprung type chain tensioner.Replaces conventional derailleur gear mech.Variable tension and position (can be used on suspension frames with varying chain length - or rigid frames.)Superlight CNC alloy body, pivot bolt and sealed pulley.Supplied with 2 springs to give "pull up" or "push down" function.Superlight CNC alloy body.Sealed bearing CNC alloy pulley.Steel no-jump guide cage.Variable tension and direction.Black anodised.96g (inc. fittings.)