Prime-Line J-4504 Steel Straight Throw Single Point Deadlock. 1-1/8" BACK SET. Hardened steel anti-jimmy bolt throw bolt with two secondary bolts which expand to lock the bolt into the strike. Secondary bolts automatically retract when the bolt is unlocked. Lock accepts standard 1-5/32" mortise key or thumbturn cylinders with AR MS-Type cam. Used to replace W&F series 6000 or comparable locks.