The kit in the picture is the bayonet mount that is made of steel and fits directly on the 1617. It requires no adapter. However, brass is the preferred material, and that material isn't available in the bayonet mount. So, you have to have the adapter, plus a second mount that fits in the adapter to use the Porter Cable bushings that are more of a standard and available in brass. I got my adapters from Bosch direct. Phone in your order to make sure you get the exact parts.