Once an E-Track is fastened to the floor of your trailer or truck, an E-Track roller fitting will allow you to use any strap to hold cargo safely in its position, without damaging the strap or wearing the load. You'll appreciate it if you haul cars, ATV's, or UTV's. It is especially helpful when hauling luxury cars, race cars, and other vehicles with limited clearance. Simply press the E-Track fitting on the roller idler and insert the hook into the E-Track slot. Slide a strap through the roomy roller. The roller moves easily in any direction, giving you the flexibility of tying the strap in any which way. This makes the roller idler fitting assembly particularly suitable for transporting vehicles without damage; the straps can trussed through the spokes of the tires or wheel nets can be used. The roller idler fitting can also be used as a second point of restraint, a simple mechanism to guide the strap. This, and the fact that the roller prevents friction with the strap, keeps the strain off the strap, extending its life and making the roller idler fitting assembly a most handy, useful gadget. NOTE: If your strap does not have a loose end that you can slide through the roller, simply unbolt the roller, place it under the strap, and replace the bolt above the strap. This roller idler is made of heat-treated medium carbon steel for superior strength and is plated with zinc, inhibiting rust. At its tallest point, it is 3.77", and at its widest point, 2.79". It has an assembly break strength of 3,300 lb. and a working load limit of 1,100 lb. When four are used per vehicle (one per tire), a collective working load limit of a fantastic 8,000 lb. results, enabling the roller idler fitting to be used with your heaviest cargo load. All products with E-Track fittings are compatible with A tracks too.