The Tillotson Mounting nuts are made for HW Model Carburetors and other modern Tillotson bodies with the built-in air filter flange. 

This makes the carburetor more manageable and easier to install and remove. The mounting nuts are installed using a 5mm hex key or Allen wrench. 

81-377 OE Tillotson Mounting Nuts fit all HW Tillotson and other newer body carburetors. Check your carburetor listing before ordering