Shimano ST-M951 is a combination of Rapidfire SL and Rapidfire Remote SL levers, designed for precise and effortless gear shifting. Here's an overview of its capabilities:

1. Gear Shifting: The ST-M951 features a Rapidfire SL lever (A) for quick and intuitive gear shifting. With a flick of your thumb, you can shift up or down by multiple gears, providing smooth and responsive shifting even under load.

2. Remote Operation: The Rapidfire Remote SL lever (B) allows you to shift gears remotely, providing greater flexibility and control. You can easily operate it with your index finger while maintaining a secure grip on the handlebars.