An arrow is a fin-stabilized projectile launched from a bow, typically composed of a shaft, a pointed arrowhead, stabilizing fletchings, and a nock for the bowstring—with craftsmen known as fletchers and arrowsmiths. Its history is ancient, with the oldest likely arrowheads dating back roughly 64,000 years in South Africa's Sibudu Cave and 48,000 years in Sri Lanka, while the earliest bow-shot arrows (about 10,000 years old) were found in Germany's Ahrensburg valley. Arrow sizes vary widely from 18 inches to 5 feet, though modern arrows usually span 30–38 inches, and arrows recovered from the Mary Rose (sank 1545) were mostly 30 inches long. Shafts historically used wood, bamboo, or reeds, but now incorporate modern materials like aluminium and carbon fibre, with their stiffness measured as "spine" to ensure consistent flex around the bow. Additionally, arrow weight is calculated using the GPI (grains per inch) system, and premium "footed arrows" are crafted by splicing two different woods together for enhanced durability.