Parts of the necklaces from the Modern Dog Tag Rock the Sky Aviator Edition have flown at altitudes of at least 10,000 feet. Plane Pieces Inc. creates these limited edition modern dog tags by cutting, shaping, and polishing pieces from actual airplane propellers. The highly polished aluminum piece measures approximately 1 _" in diameter. It comes with an oversized hole. The piece features a 24" stainless steel ball chain that you can cut to your preferred length. These handcrafted dog tags are individually unique. No two necklaces are alike. Shipping costs are $5 within the USA and $12 outside of the USA.