Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 53681 found under Guide Crosshead by Hydro Test Products Inc. The National Stock Number assigned to this part is 3655012064920, and the Federal Supply Class is 3655 Gas Generating And Dispensing Systems Fixed Or Mobile. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 53681.