SLX drivetrains seem to be an afterthought. We get it - XT and XTR are flashy and featherweight, but when it comes to workhorse components, SLX is damn near impossible to beat. Thankfully, it also comes along with trickle-down technology from its pricier siblings, and it's easy to see with the new SLX RD-M7100 Rear Derailleur that's optimized with 12-speed technology, crisp shifting, and sleek graphics that elevate standards far above what we think of when we talk about mid-range groupsets. It comes ready to take on the big-guns, with a 51-tooth capacity (a whopping 10 extra teeth above the previous version), and the flexibility to run both of Shimano's 12-speed cassette offerings. The new SLX rear derailleur features a larger, 13-tooth pully wheel for an increase in efficiency and chain management while you're riding. This partners up with advance shifting performance to deliver decreased tension when you're in the big rings. More changes happened to the pulley cage, with an added bumper that protects your pulley wheel from impacts with rocks and branches - an appreciated feature with the extra length that the derailleur hosts in order to accommodate all 12 cogs. The derailleur is built to accommodate both of Shimano's new 12-speed cassettes, the 10-51t, or 10-45t cassttes, so you can find the right gearing for your ride, regardless of you're charging full-speed through smooth ribbons of single track, or crunching up steep, seemingly endless fire roads on sky-high enduro climbs. One thing that we're thankful has stayed the same through the generations is the stabilizer switch that we saw trickling down from XT and XTR in the previous model. When engaged, this switch helps to eliminate chain slap and dropped chains by increasing spring tension. This is a valuable option for suspension systems that require chainstays and pivots located close to the rear derailleur. The RD M7100 keeps a good thing going with some of the previous model's improvements, including th...