The Vented Helmet Strap Mount Adapter for GoPro HD Hero 1 2 3 ST-04 is made of soft nylon material and allow you to attach your GoPro camera to any vented bike ski kayak or similar sports helmet. Adjustable strap design makes it suitable for most people. The strap allows your HERO camera and its quick release housing to attach to the base plate mounted on your helmet. Compatible with GoPro Hero 2 / Hero 3. Durable nylon strap is easy to install and remove. The strap adjustable size: 3.94-11.8 in.