Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 549-3815-013 found under Crystal Unit Set Quartz by Crystal Sokol Products Inc. The National Stock Number assigned to this part is 5955009591192, and the Federal Supply Class is 5955 Oscillators And Piezoelectric Crystals. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 549-3815-013.