For double gearing configurations
Weight: 225 g.
10-spd compatible

Like the 7900 mechanical derailleur, the 7970 has a new carbon fiber rear pulley cage and the new design is compatible with wider range cogsets, accommodating up to a 27 tooth cog. The differences are the fact that the unit is now driven by a servo motor instead of a cable and spring, so shifts are identical and precise every time as the computer control unit analyzes each shift.
The derailleur has a built in mechanism that will allow the body to move inward under impact to reduce the potential for damage in the case of a crash. Cycling through the shifting a couple of times allows the shifter and rear derailleur to automatically re-synchronize.

Features of the Dura Ace 7970 rear derailleur

• Carbon fiber rear pulley cage for lighter weight without loss of durability
• New geometry allows for use of 27 tooth max cog
• Servo saving feature allows derailleur body to move inward on impact to reduce or eliminate damage to the component and servo motor

For double gearing configurations
Weight: 153 g.
10-spd compatible

Lightweight, precision, and fluid performance put the SRAM Red rear derailleur in a class of it's own. Red delivers top performance thanks to a diet of structural carbon and titanium. Hybrid ceramic bearing pulleys and titanium parallelogram pivot bearing refinements further supercharge the overall component speed, accuracy, and durability.

Minimum Sprocket: 11 tooth
Maximum Sprocket: 28 tooth