This squeegee combines 3 firm-grip tools in 1: 70, 80 & 90 durometer blades for various PPF thicknesses & surfaces. Each hardness offers flexibility control: 70 for thin/delicate films, 80 for versatile use, & 90 for thicker films & bubble removal. Compact & efficient. The 4/3 is the most straightforward. It simply means that the squeegee has four layers in total, with three of them being the durometer layers and the fourth being a backing or reinforcement layer.