Recently I found myself having to remove the drain in the bath tub so I could clean it out. Like usually I'd totally forgotten how to get it out despite having put it in myself a few years back. Now that I remembered how, I thought I'd jot it down so I can remember again for next time.
The drain is a Roller Ball type. It simply lifts up or pushes down, nothing fancy.
I had thought there was a set screw under the cap which I had to loosen to remove it, but that turned out not to be the case. I think that was probably the old drain that had the set screw.
For this drain, you just twist it to unscrew it from the base. You need a pair of pliers to get enough force to twist it. Just grab the little knob on the top with them and turn. Easy as that!