Rear Derailleur Microshift MSH-RD-M21L, 6-7 speed (2/3x6/7), long cage, max 28–30T, min 13–14T, capacity 43T

Microshift MSH-RD-M21L is a rear derailleur designed for 6- and 7-speed drivetrains and intended for use with 2x or 3x chainset configurations. The unit features a long cage to increase chain wrap and stabilize shifting across a wide gear range. Engineered to work with Shimano-style systems, it supports large sprockets up to 28–30 teeth and small sprockets down to 13–14 teeth, providing a total chain capacity of 43 teeth. The derailleur is suitable for replacing worn components or upgrading gear systems on commuter, hybrid and touring bicycles.

Advantages

The long-cage design improves chain retention and maintains consistent derailleur tension across multiple chainring setups. Compatibility with common Shimano-style shift systems makes installation and adjustment straightforward for mechanics familiar with standard rear derailleur setups. The specified sprocket range and total capacity enable reliable operation with a broad selection of freewheels commonly used on older or value-oriented 6- and 7-speed bikes.

Suitable for

• Commuter bicycles with 6- or 7-speed drivetrains
• Hybrid and city bikes requiring durable, easy-to-service components
• Touring bicycles using 2x or 3x chainring configurations
• Replacement of worn or damaged rear derailleurs on compatible setups

Key specifications

• Compatible speeds: 6 and 7-speed drivetrains
• Chainring compatibility: 2x and 3x chainset configurations
• Cage length: long cage for increased chain wrap
• Maximum sprocket supported: 28–30 teeth
• Minimum sprocket supported: 13–14 teeth
• Total chain capacity: 43 teeth
• Shifter compatibility: Shimano-style indexing

How to use

Mount the derailleur to the bike’s derailleur hanger and align it according to standard rear derailleur installation procedures. Set the B-tension and high/low limit screws to match the cassette or freewheel size, and route the chain through the jockey wheels ensuring correct chain wrap. Connect the shift cable, adjust cable tension using the barrel adjuster, and test indexing across all gears, making fine adjustments to the limit screws and cable tension as necessary for smooth shifting.

Usage recommendations

Use with compatible 6- or 7-speed shifters and ensure the derailleur hanger is straight before installation. Periodic lubrication of pivots and checking cable condition will prolong service life. When pairing with larger sprockets near the stated maximum, verify B-tension to avoid contact between the upper jockey wheel and the largest sprocket.