New! What every ESR user has been waiting for... The innovative "Slakinater" tensioner! Aside from the Slakinator being "auto adjust" to always keep constant and proper tension on the chain and preventing back lash during deceleration along with chain derailment, the amount of tension itself is easily adjustable and the wider range of motion allows for a wider range of gear combinations while still using the stock chain. This part does not work on the ESR Sport, Iped, Iped2, or other hard-tire electric models.