Couplings Couplings are used to connect two joints of pipe together. Crossover, Inc. handles many types of API Couplings. As a rule, we stock enough of your common couplings which enable us to ship the same day if needed. We carry in stock J-55, L-80, N-80, and P-110. As for sizes, we carry 2 3/8”, 2 7/8” 3 ½”, 4 ½” tubing and some of the casing sizes up to 13 3/8”. Stock connections are EU 8 Rd., Nu 10 Rd., LTC, STC, and BTC. Our couplings are primarily of USA manufacture. If origin is not important, we can source other origins and sometimes beat the USA manufactured cost. We manufacture a wide range of Crossover Couplings. Couplings are used to connect two sizes of pipes, or two different dissimilar threaded parts together. We offer special clearance couplings, special clearance couplings with bevels on both ends, and couplings with the API Seal Ring Modification.