Easily fitted to the exterior of workers hard hat and securely stores critical and potentially lifesaving ID information essential in the event of a serious accident or emergency. Lightweight and 100% waterproof. Features 3M Scotchlite reflective material. Can also be fitted to clothing and other work equipment such as harnesses. It uses a "helmet safe" adhesive to fix unit to helmet. 2.75" x .05" 100/pk