The 'E' means equipment grade, a special biodegradable low viscosity high foaming shampoo that is used in many applications - car washes, bus washes, truck cab cleaning, car and van washing. Viscosity is important, so low viscosity enables it to be fed through narrow pipes commonly found in brush washes. It is used by hand (sponge and bucket) and through car, bus and truck auto-brush washes. Car Shampoo E is the best value biodegradable car and vehicle shampoo on the market.