LiftMaster 8587 / 3595 Elite Series 3/4 HP Carriage House Chain Drive W/O Rail Assembly Upgraded to the Liftmaster 8587. Same unit different design Muscular 3/4 HP heavy-duty motor designed to lift even the heaviest carriage house doors Commercial strength steel I-beam and chassis support bracket for added strength and durability Includes The Protector System Equipped with PosiLock - stops intruders by securely locking the garage door when it is down