Slim and thin-walled design for access in difficult places these are built to exceed DIN3113/ISO3318. They are made from high grade steel and chrome vanadium alloy, drop forged, hardened and treated. Each piece is factory calibrated and checked. Optimum surface treatment against rust: 2 layers of nickel plating, one of chrome. Head is offset 15° for easy use. Each spanner is clearly marked with its size.