Shimano RS35 Tourney SL-RS35 Revoshift Bike Twist Shifter Lever 3*6s 3*7s 18s 21s Bicycle Comb RS35 as RS31 RS36 - China Bike Shifter Lever, Bicycle Shifter Lever | Made-in-China.com
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