The cavity wax is Closer to Lanoguard in consistency and will wash off if used in wheelarches like Lanoguard would but never sets hard so is great underfloor and in the cavities. The ub (brown) or (uc) clear is harder wearing and ideal for arches. It's a lot thinner than bitumen underseal, whn I did my T4 years ago it lasted well and didn't crack or peel off the surface like bitumen underseal. 2 thin coats seem to work well.What the Bilt Hamber stuff like? I.e like waxoyl or more like Lanoguard?