Built with a stainless steel spring, this is the most most reliable key reel manufactured and has been tested up to a million pulls. The case is made of a strong polycarbonate, the same material as bullet proof glass. The 2-inch diameter, pocket-watch sized case is attached to a ballistic nylon strap and carabiner making it easy to attach to anything. A new carabiner has been selected for toughness. With 8 ounces of retraction force, the reel will hold 15 keys or up to 10 ounces.