Premium Air Cleaner Nuts. Available with the distinctive GM and Chevrolet Bowtie Trademarks, these chrome plated zinc die-cast air cleaner center nuts are offered in three popular styles, in both large and small sizes. The large size is recommended for 14in and 10in air cleaner kits, and the small for smaller air cleaner kits. They fit both 1/4in-20 and 5/16in 18 studs.