The sum of the lengths of the edges with a common vertex is not more than 13 centimetres. The cross-sectional area is not more than 2.5 square centimetres. The length of chips cannot be more than 6 centimetres. At least 90 per cent of the fuel should pass through a screen with 30 mm hole diameter and not more than 20 per cent of the fuel may pass through a screen with 2.8 mm hole diameter. It must not contain visible contamination (stone, earth, metal, oil, other foreign matter) or more than 5% of particulate matter (particle size less than 1 mm).