NOS SHIMANO 6 Speed SL-TY31 SIS Right Side Thumb Shifter Index Mtb Atb Fit: Fuji | eBay
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SRAM SX Eagle 12 Speed Right Hand Trigger Shifter – The Bikesmiths
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