Carbon black is broadly grouped into three types: reinforcing (also known as hard or tread blacks), semi-reinforcing (also known as soft or carcass blacks), and specialty blacks. Reinforcing grades are valued for their abrasion resistance and elasticity and are used in applications calling for good durability such as tyre treads, sidewalls, engine mounts, conveyor belts, and marine bumpers, among numerous other products. Semi-reinforcing grades are used in items requiring flexibility and elasticity, such as tyre sidewalls, hoses, belts, seals, and innerliners/inner tubes. Specialty blacks are used as black pigments and performance fillers in products such as plastic film and pipe, printing inks, inkjet toners, and paints and coatings. Specific grades of carbon black are categorized according to standards developed by ASTM International (a global standards development organization). Under the ASTM classifications, rubber grades of carbon black are designated by the letter N (for normal curing) and a three-digit designation that indicates the grade properties. Major reinforcing grades of carbon black are N110, N234, N326, and N330, while major semi-reinforcing grades are N550, N650, N660, and N772.