This is the sending unit that measures the amount of gas in your tank and relays the information to your gas gauge. Brothers sending units are constructed of high quality stainless steel. Fits the below applications blazer - 31 gallon tank79-82 250ci78-80 350ci (manual trans) suburban - 31 gallon tank79-80 250ci1979 305ci (manual trans)78-80 350ci (1978 with ca emissions) suburban - 40 gallon tank1979 250ci78-79 305ci (manual trans)78-79 350ci (manual trans & ca emissions)