Here's another one that works just as well at less than half the price. I got mine at SBE a couple years ago. Like some others here, I mostly use it in a rolling fashion to condition the tip for accepting chalk. Works great on laminated tips, opening up the leather surface without wearing it away or changing the shape.
http://www.3cushioncues.com/Microrazor_Grip_Tip_Tool/p2041797_9404709.aspx
These microrazor plates appear to have been around for a while now. Rodney Morris showed me one that he said he's had since forever. It was smaller and square shaped instead of rectangular, but it seems to do the job just fine for him.
