This is a vacuum adapter for the Bosch 1617 fix based router. You'll want to use this exclusively if you are using a festool hose, as the attachment type is designed to solidly lock in a festool hose with the cleantec end (27/32 mm). If not, use the source as it's a more generic design. It takes two M5 bolts to screw into the tool, so I'm including the finger tightening adapters that I printed, shown in the pictures if you want to improve the process of installing and removing the piece from the tool.