305mm scrub, Polypropylene block, filled very stiff Polyester Resin Set. Hillbrush offers two 305mm heavy duty scrubbing brushes, the B759 and the B770. The polyester in the B759 is 0.75mm diameter and is 63mm out. The material in the B770 is somewhat smaller, 0.60mm diameter and 41mm out. For general occasional use both are good. So, what’s the difference? In practice the B759 is better for larger areas where the surface is even and there are no dips for soil to hide in, where the larger filaments tend to skid over the top and don’t reach it. The B770 is better for spot-type cleaning on slightly less even surfaces, and for smaller areas where soiling is likely to be harder to remove. This is because the filaments will give more easily to reach dips, and there are a lot more filaments to the square inch, allowing more intense cleaning. Recommended handles ALH27, ALH7.