Standard inner valve spring lower collar, use VSC-104 for racing. These are no longer required when using our VSU-100 and VSR-105 range of silicone wire springs or ISS-100 or ISC-100 which are a slight interference fit and friction damped. Our springs have been successfully used in road and race for many years. Originally the bottom inner spring location collars were used with all dual springs to prevent breakage caused by the inner spring wandering at high RPM but modern day spring technology has overcome that.