Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 53-904-XX found under Muffler Intake by Nelson Industries Inc. The National Stock Number assigned to this part is 2990012255933, and the Federal Supply Class is 2990 Miscellaneous Engine Accessories Nonaircraft. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 53-904-XX.