QR-1 air brake quick release valve for M939 series 5 ton trucks. P/N 288251 (11602155). NSN 4820008572737.
The function of the quick release valve is to speed up the
exhaust of air from the air chambers. It is usually mounted close to
the chambers it serves. Crack pressure: 1 psi. All ports are 3/8 inch N.P.T.