The Micro-Lock protectors contour to your body under normal conditions because they remain flexible, but when they are put under impact force, like in a collision, the molecules lock up. This locking of the molecules reduces the energy of the impact that gets passed to your body by increasing the amount absorbed by the protector. This process is similar to other armor, but the microlock works in a wider range of temperatures, so is less likely to break or snap in very cold conditions. They also are made in a common size, so will fit into a wide variety of jackets.