INSTALLATION-Our package comes with 1 door knob lock and 3 keys. This knob set can be used for left or right-handed doors. DURABLE DESIGN - The heavy-duty construction of these door knobs allows them to be strong, strong and long-lasting. The sturdy knob design prevents rattling and breaking that can occur with inferior mortise door knobs. The chrome finish adds a stylish touch to your home or office. Function - Entry door handles feature a small turning knob on one side to lock the door and a mechanism lock and key on the other side of the door. SECURITY - These chrome door knobs provide extra security with the lock and key mechanism. They are ideal for home offices, bedrooms and interior porch doors as they provide optimum security. Specification Material: Stainless Steel Color: Silver Size (L x W): approx. 170 x 75mm/6.7 x 2.95in Center distance: approx. 60mm/2.4in (Type A ), 70mm/2.8in (Type B) Suitable door thickness: approx. 35mm to 45mm/1.4 to 1.77in