Cal Am offers Schedule 40 Duct Couplings in five popular sizes ranging from 2 to 6 inches in diameter and manufactured in accordance to application requirements listed in NEC Article 347 and 370 UL514, Mil-C-23571, Federal Specification WC 1094, ASTM F513-89, and NEMA Standards. All of our PVC connectors are produced from the finest grades of high-impact Polyvinyl Chloride using state-of-the-art manufacturing techniques.