Shimano Revoshift SL-RS35,7 Speed Bike Right Shift Lever for Mountain Bicycle
shimano Revoshift SL-RS35 3X6s 3X7s grip Twist Shifter 18S 21s MTB Bicycle Bike Shifting lever - AliExpress
My daughter's Trek came with a 6-speed Shimano Revoshift SIS Index. It's a new bike. She can shift to higher gears easily but does not have the grip strength to shift back