- Universal design, you can fit this baseball bump cap insert into different cap types, satisfy your various needs. insert - Sturdy interior, stronger structure to provide better and lightweight head protection. safety bump cap insert - Can protect bump cap from bumps, scrapes, shocks and other head injuries. hat shaper insert - Easy to operate and to install with the simple structure, to provide you with a more relaxed way of modification. safety hat insert - Fine workmanship, durable and sturdy, not easy to wear or tear, you deserve to have one. safety caps liners