The Box Four shifter's main features aren't strikingly different from Box Three's. The key difference is its 8-speed platform. We've chosen to modernize the 8-speed in much the same way we did the 9-speed for Prime 9. Just like the Prime 9, the Box Four shifters take advantage of the "less is more" theme and exploit durability, simplicity, and reliability. Available as a multi-shift (pull several gears at once) or single-shift shifter (a sound choice for e-bikes). SUPPORT MATERIAL Prime 9 Technology™ View Prime 9 Drivetrain Compatibility Manual How is the Ebike variant different? View Prime 9 Comparison Chart View Prime 9 E-Bike Comparison Chart Why Prime 9?