1、Fine‑tuning knob, by rotating the fine‑tuning knob to change the length of the wire tube within a certain range, adjust the position of the flywheel and the chain, effectively solve the problems of gear adjustment, unsmooth up and down gears, abnormal chain oil noise, etc., and repeat the fine‑tuning to achieve 2、H and L main body adjustment screws, H and L are positioning screws. The adjustment of these two screws is to ensure that the chain is between the largest and smallest pieces of the flywheel. H is the high position and L is the low position. 3、Plastic steel main material, light weight, precision, high strength and durability, steel guide plate, precise and direct force transmission; high‑quality PA nylon wear‑resistant plastic guide wheel, quiet and smooth, reducing chain wear. 4、Fine-tuning screw, H/L adjusting screw, fine-tuning screw tension screw, variable speed adjustment is more precise, and the micro deformation is smaller. 5、Tension screw, chain tension screw, effectively adjust the length of the chain in order to achieve the ideal speed change effect. 6、Long-leg guide plate design, strong compatibility, fully compatible with 8/9/10 speed. Item Type: Bike Rear Derailleur Material: Plastic Steel Main Material + Steel Guide Plate + Wear-Resistant Plastic Guide Wheel Product Size: Approx. 152.8 x 70mm / 6 x 2.8in Weight: Approx. 268g / 9.5oz Applicable Speed: Suitable for 8 / 9 / 10 Speed Installation Method: Direct-Mounted Eye Shift (The Frame Needs a Rear Derailleur Hook) Total Value of Tooth Replacement: 45 Teeth Features: Lightweight, Precise, High-Strength, Silent Pulley 1 x Bike Rear Derailleur