Mack 691GC225M2 Relief Valve PAI 2653CROSS REFERENCE: 63AM28 691GC225M2 20706354 APPLICATION: Mack Aset E tech E7 Multiple Use Application. DETAILS: Open at 54 psi. M15 x 1. 5 x 5 8 18 threads. BRAND: PAI 2653 Mack 691GC225M2 Relief Valve PAI 2653. Aftermarket truck parts and truck repair parts. Maintains pressure balance and ensures consistent valve response. All components are proudly manufactured in the U. S. A. by PAI Industries Inc., an ISO9001 certified company with over 50 years