1.Gentle shifting The teeth of the 7 speed bicycle sprocket with 13 28 teeth are 13 teeth, 15 teeth, 17 teeth, 19 teeth, 21 teeth, 24 teeth, 28 teeth. The positioning slot for high speed shifts ensures even load, smooth and powerful operation, short shift transmission time, less noise, smooth shifting and effortless driving. 2.EXCELLENT CRAFTSMANSHIP Our bicycle chain wheels are made of high quality stainless steel, finely tempered and hardened, with a rustproof surface galvanization treatment. It has high hardness, wear resistance and durability, is not easy to rust, has a long life and avoids frequent replacement. 3.Unique design: the angle and height of the steel teeth of each part of the flywheel for bicycle positioning differ slightly. This allows the chain to switch up and down faster and more precisely. For this reason, the different shape of the teeth of the bicycle flywheel is a characteristic feature and not a quality problem. 4.Precision thread: the flywheel of the bike is polished with high precision machine tools, the threads are clear and firm, the high precision threads ensure a firm connection with the bicycle hub, shifting feels good and makes your ride easier.