High-purity needle valves have a body and stem consisting of PFA (polyfluoroalkoxy alkanes), an impact-resistant and highly corrosion-resistant polymer with a nonstick surface that prevents bacteria growth caused by residual media within the body from contaminating the valve and system line. They're used in cleanroom applications, such as pharmaceutical and semiconductor manufacturing and laboratory settings. They start, stop, measure, and precisely throttle system media flow rates. Flow rates increase and decrease depending on the needle-shaped plunger's position relative to the seat within the housing. Flow increases as the valve's plunger is lifted away from the seat within the housing and flow decreases as the plunger is lowered closer to the seat.