microSHIFT M21 Rear Derailleur 6/7-Speed Long Cage Claw Hanger

Affordable replacement rear derailleur for older 6 and 7-speed bikes using claw-style hanger mounting.

The microSHIFT M21 rear derailleur is designed to bring older mountain bikes, hybrids, comfort bikes, and recreational bicycles back to reliable shifting performance without expensive upgrades. Built for compatibility with Shimano 6 and 7-speed systems, the M21 uses a long cage design to support wide gearing ranges while including a dropout claw hanger for frames that lack a built-in derailleur hanger.

This makes it an excellent repair solution for older bikes, department store bikes, and many entry-level recreational bicycles still in active use.

Key Functional Details

• Compatible with Shimano 6 and 7-speed shifters
• Long cage design supports double and triple crank setups
• Supports cassette/freewheel cogs up to 32T
• Includes dropout claw hanger attachment
• Compatible with many older bikes lacking replaceable derailleur hangers
• Durable composite and steel construction
• Great repair option for budget drivetrain restorations

Technical Specifications

• Model: M21 Rear Derailleur
• Speed Compatibility: 6/7-Speed
• Compatibility: Shimano Road and Mountain Systems
• Cage Length: Long Cage
• Largest Supported Cog: 32T
• Chain Wrap Capacity: 43T
• Mount Type: Dropout Claw Hanger
• Color: Black
• Weight: 316g

Compatibility & Technical Notes

• Compatible with Shimano-compatible 6 and 7-speed shifters
• Designed for bikes using claw-style derailleur mounting systems
• Ideal for frames without integrated derailleur hangers
• Supports many freewheel and cassette-based drivetrains
• Maximum cog size is 32T
• Not compatible with modern 8/9/10/11/12-speed indexing systems
• Derailleur hanger alignment strongly affects shifting performance

Service / Ownership Context

• Excellent repair solution for older bikes still worth maintaining
• Common replacement for bent or damaged rear derailleurs
• Claw hanger simplifies repairs on bikes without replaceable hangers
• Ideal for economical tune-ups and drivetrain refreshes
• Often installed alongside new cables, housing, and chain replacement

Fit & Use Signals

• Good Fit: Older mountain bikes, hybrids, comfort bikes, recreational bikes, department store bikes
• Not A Fit: Modern 9-12 speed drivetrains, direct mount hanger systems
• Use Case: Budget drivetrain repair, derailleur replacement, older bike restoration