The washer has an outer diameter of 5-3/4" and an inner diameter of 4". It is designed to be compatible with all Pioneer systems that utilize round coil springs, such as the G1500 series, EDD1500 series, HR1500PTO, HR1500PTOAL, HR1500H, HR1500HAL, HR1500E, and HNR1500EAL. However, it does not fit the 1000 series of Pioneer construction systems.