Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 21399 found under Muffler Exhaust by Walker Mfg Co. The National Stock Number assigned to this part is 2990008462942, and the Federal Supply Class is 2990 Miscellaneous Engine Accessories Nonaircraft. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 21399.