Zero reference offset spacer for glass plate printing.

I'm just making my first foray into glass plate printing and I realised I needed to adjust the Z axis zero point to compensate for the thickness of the glass, so here's a little device to do just that. I designed it for my Wanhao Duplicator 4 which I believe has the same layout as the Makerbot so should work for either. Nice and orange so I can easily see when it's in place.