I bought this tool to help me set up my brakes better. I have mostly mechanical discs but three setups are hydraulic. I was tired of the inferior power that you get after changing a tire for the most part. For hydraulic brakes that have a pair of opposing pistons, this tool is amazing and while others indicate you can just use two feeler gauges, don't listen! It is tight in the brake area and having a two bladed feeler gauge (which this is) works amazingly well. I just put the unit in the brakes, bungie the lever such that there is a lot of pressure on it, loosen the bolts so that they are about two turns off of tight. At this point, I can rotate the tire a small amount and the caliper clicks on the bolts back and forth a little. I next tighten the bolts by 1/4 turn at a time until both are tight and remove the bungie and tool and hello stopping power.For mechanicals that only really have one moving element, this tool is almost worthless. Just set the fixed side about .020 - .030, then adjust the cable length such that the caliper arm is at about 75% of full stroke (100% is completely relaxed and 0% would be the cable pulled all the way in by the lever). Next, bungie the lever down hard and do the bolt loosen/tighten thing like it was a hydraulic system and you are good.The difference between Pro and Shmoe is the tools and knowing the best practices for maintenance. You paid for good brakes, now it is on you to keep it dialed. This tool can help.