Marketing InformationSpears® transition fittings are designed primarily for adapting plastic-to-metal systems. These fittings, especially the special reinforced (SR) female plastic thread-style, can also be used for superior strength in make up of plastic threaded joints. Spears® offers a variety of transition adapter fittings specified below. All have standard ASTM socket sizes for IPS pipe and NPT threads, except for the gasket sealed-style that uses a straight thread with elastomer seal. All other threads should be assembled with a quality-grade thread sealant that is compatible with plastics.