A wall bushing made to allow you to pass Ethernet Cables through a wall that is only dry walled on one side. 

Required a 2" hole in drywall to allow main piece through the wall and then you thread the other piece onto it and tighten it by hand. Minimum drywall thickness is ½" but can be secured onto 1"00 thick wood as well.

ADDED A NUT WITH A STAND OFF TO ALLOW FOR THINER SHEETS OF DRYWALL OR OTHER SUFRACES