Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 21A 241 found under Nut by Mack Trucks Inc. The National Stock Number assigned to this part is 5310007343409, and the Federal Supply Class is 5310 Nuts And Washers. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 21A 241.