CERTAIN PARKER BRASS 90 DEGREE SINGLE CHECK VALVES WHICH ATTACH TO THE SUPPLY PORT OF A BENDIX SR-7 SPRING BRAKE MODULATING VALVE SOLD AS ORIGINAL EQUIPMENT AND ALSO SOLD SEPARATELY AS P/N 5010889. AFTER PROLONGED USE OF THE PARKER SCV, THE VALVE BODY RETAINER MAY BECOME EXCESSIVELY WORN AND EVENTUALLY BREAK APART. PIECES OF THE PARKER SCV CAN BECOME LODGED INSIDE THE SR-7 SPRING BRAKE MODULATING VALVE, POTENTIALLY CAUSING EITHER LEAKAGE OUT OF THE SR-7 VALVE OR PREVENTING AIR FROM PROPERLY EXHAUSTING FROM THE SR-7 VALVE.