Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 3537.MOD ITEM 37 found under Spacer Ring by Cat Pumps Corp. The National Stock Number assigned to this part is 5365012997450, 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 3537.MOD ITEM 37.