John Guest Acetal Copolymer Tube Fitting, Reducing Straight Union, 5/16" x 1/4" Tube OD (Pack of 10) Reducing straight union for connecting and disconnecting two inline pipes of different diameters more easily than couplings Accepts nylon and polyurethane tube fittings Made of acetal copolymer plastic for low moisture absorption and high tensile and flexural strength Working pressure of up to 150 psi Meets NSF/ANSI standards 14, 51, and 61 for quality assurance