This product is a high-performance racing block designed for Honda EX5, EX5 Dream, and Wave100 motorcycles. It's specifically categorized under Class 1 racing modifications and indicates it's ready to be skimmed or machined to achieve optimal performance. The product offers a range of cylinder bore sizes, including 53mm, 54mm, 55mm, 56mm, 57mm, and 58mm, giving users options for different levels of engine displacement upgrades for racing purposes. The 'Hhm Racing' suggests it's manufactured or endorsed by a racing-focused brand.