Replacement suspensions replace worn or broken inner suspensions in hard hats and bump caps. They typically come in ratchet or pinlock forms. Ratchet suspensions use ratchet wheels to adjust fit quickly, while pinlock suspensions use a series of selectable pinholes to adjust fit. Replacement suspensions with more suspension points are better at spreading force and increasing comfort. They are typically made of high-density polyethylene (HDPE) because it is a strong, lightweight material.