If you have metal doors to protect then this 3/4 inch recessed contact is what you'll want to buy. This recessed contact features a protective collar that puts space between the magnet and the metal of the door itself. We have found that if you try to use a regular recessed contact for metal doors; the magnet will lose its strength over time.
You can also use this contact for any application where a larger contact is needed. Whether using on metal doors or installing or replacing contacts with ¾ inch diameter holes; you find this very useful.