The REDS Glow Plug and Clutch Wrench is a great accessory for your pit bag. Featuring a 5mm Hex, 8mm socket and 10mm socket wrench. All of these sizes are crucial for your nitro engine. The 8mm socket is great for installing and removing glow plugs and the 10mm socket is perfect for installing and removing clutch nuts. The 5mm hex is perfect for working on 1/8 pivot balls and other applications. Package includes one clutch wrench.