The Spool Valve consists of two body segments, (an air cylinder segment and an air cylinder cap) and a balanced spool shaft. The Spool Valve is based on a balanced spool design to creat a fast On/Off fluid dispensing funtion that is not affected by material input pressure. The hardened spool slides in Teflon seals and is suitable for use with materials having a viscosity of 100 CPS to over 3,000,000 CPS at pressures of up to 2,500 PSI. The spool action displaces a portion of the material back into the nozzle during shut off. This creates a "suck-back" anti-drip feature. Typical materials: Grease, RTV Silicone Sealant, Solder Mask. 3/8" NPT inlet.