Needle valves are usually used in flow-metering applications, especially when a constant, calibrated, low flow rate must be maintained for some time, such as the idle fuel flow in a carburetor. Needle valves sometimes referred to as plunger valves. A needle valve has a relatively small orifice with a long, tapered seat, and a needle-shaped plunger on the end of a screw, which exactly fits the seat. These needle valves are an ideal option for isolating or throttling applications. The self centering, non rotating stem ensures perfect seating. The rigid design gives repetitive bubble tight shut off, easy.s. Our range of needle valves has been designed with durability and performance in the spotlight. These needle valves are available in a variety of sizes (1/4, ½, 1/8 inch). Our range of needle valves has been designed with durability and performance in the spotlight. These needle valves are available in a variety of sizes (1/4, ½, 1/8 inch).