The bontrager xr silicone grip the xr silicone mtb grip features a proven design with a consistent feel and race ready weight that is ready to tackle any trail this unique silicone and foam blend absorbs shocks and maximises grip to add comfort confidence and a bit of durable class to any mountain bike bontrager xr silicone grip features the silicone foam blend provides excellent grip and shock absorption the simple design maximises durability and minimises weight 32mm