About this item Application-- The O ring & C ring is well-designed by us and the size is 3/8 inch. Fits for Milwaukee Brushless Impact Wrench. Easy to install-- The installation is pretty simple & easy and you can install it just few minutes.Step1-press the O ring into the wrench directly refer to our instruction. Step2-put the C ring into the installation tool(The hole for the mounting tool is 3/8", which makes it just the right size to accommodate the C-ring). Step3-Then insert your wrench into the installation tool at a 45 degree angle. .