Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number P21-0528-04 found under Spacer Plate by Hardigg Industries Inc. The National Stock Number assigned to this part is 5365015035355, and the Federal Supply Class is 5365 Bushings Rings Shims And Spacers. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like P21-0528-04.