I think I'm remembering this correctly ... Flip the top half over. The tab on the float will press on the needle. Measure from the edge where the gasket goes (supposed to have the gasket on it, I believe) to the highest point on the float. Should be 1.26-1.29 inches for rubber float (1 and 9/32 would give you 1.28"). Or 1.2 to 1.24 inches for nylon float (1 and 7/32 would give you 1.22") if you're using standard and/or non decimal measuring tools.