I finally selected this Vigo product after others failed to arrive intact. The hardware is perfect and well made. Surprisingly the engineering is to perfection with the metal parts and very strong even though it is minimal hardware (which is what we wanted for a frameless door). 
The width really does require 4”, so I had to add a stone sill to my tub. One negative is the instructions, which were VERY good with detail, except they are written for both models (tall door for shower-only, and a shorter door for tub). Dimensions for drilling the mounting screws at a specific height were given from the floor for the longer door, but NOT for the shorter door from the tub level. This took some creative, complex measurements to ensure the drilling (through brand new tile) was done exactly right. No room for error.