FreeDeePee BedSlider GT2 - For USA Flat washer

This is a simple modification of litwan's Bed Slider for Makerslide used in his FreeDeePee 3D printer. I modified the ID (11.8mm) of the part to accept a standard 6mm flat washer (6.5x11.8x1.5) from HomeDepot. The original design requires a (7x11x2) flat washer that I could not find anyplace.