Shimano SL-RS45-6 Tourney 6 Speed Revoshift Right Hand Twist Shifter With Cable | eBay
Shimano Bicycle Derailleur RS35 RevoShift Easy Gear Changing Shift Lever 3*6/7 18/21 Speed MTB Mountain Bike Folding / City Bike|Bicycle Derailleur| - 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