Made from high-strength glass-reinforced Marelon. Dimension "A" indicates pipe thread size. All elbows sold in U.S.A. have straight pipe threads. "M" models have male threads, "F" models have female threads. Model HECM 20 A 1-1/4 B 1-1/4 C 7/8 D 2-3/4 E 3-5/16