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 24 A 1-1/2 B 1-1/2 C 1-1/16 D 3-1/4 E 2-3/4