PD-7, PD-9: Differences between the PD-7 and PD-9 April 12, 2023 08:47 Updated Follow The only difference is the size. PD-9 is 10" diameter and PD-7 is 7.5". Another difference, not affecting performance, is the texture of the pad. Related articles PD-9: Specifications TD-50KV and TD-50KV2 differences