NIBCO® 1" X 3/4" Sweat Copper Reducer Coupling at Menards®
Amazon.com: Brass Pipe Fitting Coupling-1/2" x 1/2" NPT Female Chrome Plated Finish Brass Pipe Fitting Coupler with 1 Roll Copper Joint Thread Sealing Tape for Home Plumbing Pipes (1pcs-Chrome Plated) : Industrial
Coupling (piping) - Wikipedia
What do you mean by coupling in plumbing? - Quora
Standard Flexible Couplings | Fernco - US
QuickFitting 3/4 Inch Push On Coupling | Patented Design for Superior Sealing | Push to Connect Brass Plumbing Pipe Fitting | for Copper, PEX and CPVC | 5-Pack - Amazon.com