There isn't one. Only A Mach2(inch), and a Mach2(mm).
On a side note...You, Tweakie, are the reason I am spending every waking hour of free time working on my CNC. The things you have done are truely an inspiration to thoes of us who want to do more than just cut signs on our routers and mills. My biggest issue I have is after I FINALLY figure out somthing new to try, (Tangential cutting, Laser etching, 4th axis stuff etc...) I have no real need for it and end up looking for something new to try. Please continue to give me something to shoot for. Thanks, Andy