Liftmaster LA500 Primary 24VDC Actuator Arm only
Liftmaster LA500DC Installation Manual (click here)
I purchased this to replace the one that was failing/failed. Easy replacement DIY. My only star remaining was that it does not have the blue LED on/off actuator light like the original.
The Loadmaster gate operator I ordered arrived in perfect condition. My total experience with Gatehouse from start to finish was exemplary.