The reason we at Blockley manufacture rim bands, rather than sourcing what is already produced, is because often the available rim bands are feathered in thickness at the edges. We find this unacceptable especially since the material they use also goes hard over a period of time, so these tapered edges act like razor blades which can slit the inner tube. They are also often a dark fairly inelastic material.
The Blockley rim bands on the other hand are made from a softer compound and the edges are square cut at the full thickness, which stops this problem ever occurring. This level of attention to detail (as with all our products) really is important. Rim bands are only necessary in the wheel well of wire wheels, where exposed spoke heads are present. Insulation tape is not adequate! (this also goes hard and cuts the tube) as well as being too thin, so always use Blockley rim band. We make bands in many diameters and widths, including the extra wide rim bands for Borrani wheels.