Brown and Barlow (B & B) carburettor float chamber top feed nut solder tail for 1/4 inch copper pipe. 9/16 inch x 24TPI thread. Suits 1915 model.Original part number012 - petrol union nut (1916-23); 112 (1924-26)013 - petrol union (1916-23); 113 (1924-26)