The microSHIFT RD-M5185M Acolyte Rear Derailleur 8 Speed is exclusively compatible with microSHIFT Acolyte shifters and Acolyte 12-42T/12-46T 8-speed cassettes. The SpringLock chain retention system with direct path cable routing helps to increase the efficiency of shifting and engagement. The cage size is medium and this is the Clutch version. To engage clutch, turn the engagement bolt clockwise until it clicks. There's no way to overtighten the bolt. To disengage the clutch for wheel removal, flip the switch. Available in Black.