Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number BT400-42-1 found under Heater Duct Type Portable by Engineered Air Systems Inc. The National Stock Number assigned to this part is 4520000544716, and the Federal Supply Class is . Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like BT400-42-1.