Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 20253 ASSY 20253 found under Valve Safety Relief by Tyco Valves And Controls Lp. The National Stock Number assigned to this part is 4820013687507, 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 20253 ASSY 20253.