Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 387990 found under Valve Seal by Simpson Lawrence Ltd Johnson And Evi. The National Stock Number assigned to this part is 4820011943578, and the Federal Supply Class is 4820 Valves Nonpowered. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 387990.