Originally Posted by
isuzurover
For what vehicle?
MD lockers have the advantage that they have no rotating air seal, and are designed to operate on vacuum (-14 psi) or ~15 psi compressed air. Once locked, they will stay locked (held in by detent) until you unlock them. The light only lights up once they are fully locked. I believe MR Auto is only selling the Salisbury version these days?
ARB on the other hand need ~70 psi to operate, only stay locked while they have air pressure and the light just tells you you have flicked the switch.
AFAIK Ashcroft locker were designed after the guys at Ashcroft had ~20++ years experience installing, modifying and improving ARB lockers. They tried to give ARB design improvements but they were not interested, so instead they developed an "improved" locker.