Aqualine QCK-075 - 3/4" Replacement Quick coupling key: Key threads into top of quick-coupling valve to provide water access. Durable brass construction. Key is inserted into quick coupler valve to allow water flow. Threaded for 3/4" hoses and is internally threaded for 1/2" impact sprinklers. For use with the 3/4" water hose. *You can also add a brass swivel elbow for 360-degree, kink-free watering with your hose.