SHIMANO TOURNEY Left Shift Lever 3x7/6-speed | SHIMANO BIKE-EU
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
Shimano Revoshift 7 speed gear shifter
Shimano Revo 7 Speed Twist Shifter – Infinity Cycle Works