The hope tech 3 e4 disc brake is designed for aggressive trail and enduro riding and with its revised caliper and excellent tech 3 lever the e4 offers riders all of the power and adjustability they need this hope tech disc brake has 4 identical 16mm phenolic pistons which means there is a larger surface contact with the disc resulting in a better more powerful stopping power hope have made sure they keep the same key features of the tech evo master cylinder on the e4 brakes and have worked o