Each door holder assembly consists of a floor or wall mounted heavy-duty electromagnet, a self-adjusting and pivoting armature, and all necessary mounting hardware. All models are field selectable to operate on 12 VDC, 24 VAC/VDC, or 120 VAC input voltage. Convenient screw terminals are provided for field hook-up. All holder models are UL listed.Optional Extension rods are available, to extend the armature projection, for installations where a wide standoff distance between the electromagnet and armature mounting locations exist. DynaLock 2800 Door Holders each provide 30-45 lbs. of holding force, allowing manual door closure when electromagnets are energized.