USB microscope stand

This is a fairly simple stand for cheap USB microscopes like this :
http://www.ebay.com/sch/i.html?_odkw=usb+microscope+500x&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xusb+microscope+50x+500x.TRS0&_nkw=usb+microscope+50x+500x&_sacat=0

I find the stock stand not very efficient therefore I designed this one.
It is stable and allows to easily change distance between object and lens.