Designed with grooved pins to hold the camshaft pulley stationary while loosening and tightening the center shaft bolt. The rear pulleys on these models are in very close proximity to the shock tower making removal and replacement difficult without this locking device. WARNING: This product can expose you to chemicals which is [are] known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.