Installing a Shimano 12-speed cassette with a 9T cog? The TL-LR21 Lock Ring Tool 9T is the shop-grade tool designed specifically for the job. It delivers a precise fit on Shimano's unique 9T lock ring, helping us get a secure mount without slipping, stripping, or rounding things out. Built from durable steel for daily use, it's the kind of purpose-built tool that belongs in every well-stocked bike bench. No guesswork, no frustration-just a fast, clean install every time.