These SurfPrep 6-inch backup pads are a must - have for anyone involved in sanding projects. Whether you're a professional woodworker or a DIY enthusiast, these pads will make your sanding tasks a breeze. They are suitable for sanding various surfaces such as wood, metal, and plastic. The pads come in different types (Hook & Loop, J - Hook, and PSA) to meet different needs. With a thread size of 5/16 - 24, they are designed to work perfectly with SurfPrep 6 - inch sanders.