True Union design permits installation or repairs without expanding pipeline. Rugged square body and bonnet are of solid thermoplastic for maximum corrosion resistance. Uniquely designed body and bonnet together with diaphragms of new sealing designs by the state-of-the-art computer aided analysis for superior sealing. Weir design for excellent throttling. Full vacuum rated. Bubble-tight sealing, even in applications such as slurries or suspended particles.