If you’re in search of a responsive left shifter for your 9-speed mountain bike drivetrain, the Shimano Alivio SL-M3100 could be a great option. It’s equipped with Rapidfire Plus technology that allows quick shifting, making it easier to downshift three gears in just one stroke. In addition, the shifter has an optical gear display located below the handlebar that allows riders to easily see their gear position at a glance. With these features, the Shimano Alivio SL-M3100 left shifter could be a reliable and efficient addition to your mountain bike.