This door opener adapter is designed to fit a 47mm door knob, allowing you to open the door using your arm (sleeve) instead of your hand. Mounts with 3mm machine screws. You can add some glue to the knob for extra friction to prevent slipping.
The push model is designed to work on its own. The pull model has an extra hole for attaching the arm guard to help pull the door open.
Both handles are designed to work on their own.
Both handles are designed to fit either way on a door (left side or right side). Pull style 2 uses less plastic and the arm guide is more stylish.
Be safe, be healthy and wash your hands often.