Review on SRAM Eagle GX NX 12 Rear Derailleur Adjuster & Chain Gaps Adjustment Gauge Tool for Hiking, Road, City, and Mountain Bicycles - Perfect for Racing Bicycles by Brian Lee

For a perfect setup of a full suspension bike it is recommended that the rear suspension has some sag. Since I was alone in the adjustment, I bled the shock completely, fully open and lowered to 25% with one hand, and checked the gap with this tool with the other hand. . I did this at night and there wasn't enough light in my garage to see things well, so I set up a flashlight to shine directly on the switch and it worked. It took me a few minutes to get it right but I did it perfectly and now the shift seems very smooth.