I recently got this WM-10, which incidentally is identical to one I had when I was about 14 years old (possibly THE best Christmas present I ever got!). Sadly this one doesn't work so well, even after a new belt (the inversion wheel is really sloppy). But what I'm curious about is this plastic thing - is this just part of the packing materials? Why the slots for the belt clip? Maybe mine originally came with this piece, too - but I have no memory of it.