Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number ST4M166-6-004 found under Bushing Sleeve by Master Machine Products Corp. The National Stock Number assigned to this part is 3120003452147, and the Federal Supply Class is 3120 Bearings Plain Unmounted. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like ST4M166-6-004.