Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number B566S-3.75PSI found under Head Safety Pressur by Henry Technologies Inc. The National Stock Number assigned to this part is 4820010356618, 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 B566S-3.75PSI.