Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number SYM520.1 MOD found under Switch Push by Hiller Companies Inc The. The National Stock Number assigned to this part is 5930015516319, and the Federal Supply Class is 5930 Switches. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like SYM520.1 MOD.