A. This engine cylinder kit is designed for mini motorcycles. Its model is 44 - 6, with a diameter of 44 mm. It is compatible with mini motorcycles and is an ideal accessory for building mini sports cars. B. It has 2 ring grooves. The piston ring structure uses a slotted oil ring, and the cross - sectional shape is a barrel - faced ring. This unique design helps the engine run more stably and smoothly, effectively improving the overall performance of the mini motorcycle. The pin hole × pin length is 37 mm. The precise dimensional design ensures a perfect fit with the mini motorcycle. C. Whether you are a riding enthusiast seeking excitement or a player keen on modifying mini motorcycles, this engine cylinder kit can meet your needs. D. It will bring a new power experience to your mini motorcycle and allow you to fully enjoy the fun of riding.