a designation for a type of valve produced by the Americanvalvecompany RP&C (RP&C stands for Reading-Pratt & Cady). TF is an abbreviation for Teflon, a trademark for a plastic material with nonstick properties that is used in insulation, cookware, etc. It remains stable in extreme heat and cold and does not react with other chemicals. 301 TF denotes a valve that utilizes a ball (that sits on a Teflon base within the valve) to check a flow of liquid.