Type-21/21a ball valves are corrosion resistant plastic manual true union design quarter turn valves with hyperbolic flow characteristics, low pressure drops and reliable sealing. They are typically used in on/off applications and are offer relatively poor flow control. They are excellent for use in clean fluid service applications with very little to no suspended solids. Type-21/21a ball valves are well suited for a wide variety of fluid flow applications. True union ball valves can be lifted from the line without having to move the piping simply by loosening the two union nuts. The valves can be disassembled, and parts may be replaced. They can be pneumatically or electrically actuated.