Coilover kit - BC Racing - 2 Way Adjustable - ER Series - MR-S ZZW30BC Racing ER Series Coilover kit for MR S ZZW30 BC Racings 2 way adjustable coilovers are the external reservoir ER Series with separate compression and rebound damping adjustment. The ER Series coilovers for the MR S bring with them the high quality and unique features seen on the BR and RM type but have the additional benefit of external reservoirs and the ability to allow the end user to individually adjust and set compression and rebound damping