This is a tool used to screw in the caulking nut (energizes the nitrile gasket on the topside of drain) on a shower drain. Drain was for a 3" pipe. The “no caulk shower drains” should all be fairly universal. The one I installed was similar to this Oatey® 140 Series / 101 PNC Series Plastic No-Calk Shower Drain | Oatey. 

The hex (3/8") stripped out on me, but using a pair of channel locks on the cross of the tool worked just fine.