This is the exact product that I used for my large WWII Bombed City board set. The pieces supplied are cut from MatBoard which is .052" thick (just under 1/16" or 1.3mm) and they make up the sidewalk areas and bases for the buildings. Your roads will be the base board that you supply, I prefer 1/2" MDF for my base boards but you can use whatever you like.
For these pieces to work perfectly you will need a base board that is cut to exactly 20" x 20" (508mm x 508mm). The way these work is simple; first paint your entire base board the color you want your roads to be, then paint these pieces a concrete color and then glue them on leaving 1" (25.4mm) exosed between each piece to represent the roads.
You will notice that this setup is meant to be used in multiples of 2 boards, the road on the right side of the layout drawing (see photos) is only 1/2" wide so that when two boards match up there is a 1" road with a traffic circle (roundabout).
Note: some of the product photos show my city boards in which I used 4 of these kits to create 4 boards that fit together. Naturally, buildings shown in photos are not part of the kit.