Water swivel adapter. I have used water cooled equipment before and the design of this adapter is quite poor. There is no seal at either the point of attachment to a grinder not is there any seal around the shaft to limit water egress to the tip and into the center of the core where it is intended to go. Since there is no seal, water actually flows through the bearings. Somehow I have doubts these bearings are made for water contact. Furthermore, the bearings are welded into place which likely distorts the raceways which will inevitably lead to early failure and, since they're welded into place there is no replacing them. Essentially this item is not a professional grade piece of equipment.