Plated steel chain and Diecast keeper provides increased security while allowing viewing and ventilation. This chain door lock can be unlocked with key from outside or inside of the home. This lock engages by allowing the bolt to slide into the keyed mechanism to lock, and it uses a B1 keyway, ilco (1098M). Finish: Polished Brass Material: Steel Length: 3-7/8 In. Width: 1-1/4 In. Bolt Activation: Keyed Chain