[Package Includes] : (6 Sets + 6 Sets) 1/2" and 3/8" Impact Wrench Retainer Rings & O-ring + Anvil Tool [ 1/2" Compatible with ]: 1/2" Standard Type Impact Wrench, Meet-OEM Standard; 1/2" Square Drive Electric Wrench and Pneumatic Wrench are Suitable for This Kit. [ 3/8" Compatible with ]: 3/8" Standard Type Impact Wrench, Meet-OEM Standard; 3/8" Square Drive Electric Wrench and Pneumatic Wrench are Suitable for This Kit. [Note]： Specifically designed to fit type 1/2" and 3/8" cordless impact wrench. [ Specifications ]: Size: about 1/2 inch and 3/8 inch; Color: Black; Material: Carbon Steel, Rubber [ Anvil Retaining Ring Install Instruction]： Step 1: Install new o-ring to your wrench. Step 2: Put retaining ring into install tool recess. Step 3: Insert the anvil into the retaining ring with 45° thrust. Step 4: Push and bring the anvil perpendicular.