Shimano Tiagra SL-4600 10-Speed Right Flat Bar Rapidfire Plus ShifterShimano Tiagra SL 4600 10 Speed Right Flat Bar Rapidfire Plus Shifter. The Shimano Tiagra SL 4600 offers Rapidfire Plus shifting with 10 speed road drivetrain compatibility. Optical gear display indicates gear position with just a glance RAPIDFIRE PLUS technology is suited to quick shifting giving riders the ability to downshift three gears in one stroke 2WAY RELEASE means shifts can be released by pull of the index finger or push of the thumb INSTANT