This is double bearing, Delrin, V wheel. It uses (2) 5×16×5 bearings and a precision shim washer. It has very low runout, so it will run wobble free. The mounting is very simple with only a 5mm hole required.
An easy way to tension the wheels against the rail, is to use eccentric spacers for the wheels on one side of the carriage.
Here is the technical drawing for the V-Wheel.