Wow. What a great set of wrenches. I was given a smaller set of the non-flex head version of these wrenches several years ago as a gift and have used them so much, I decided to buy this larger, flex-head version. These things really let you get into tight spaces (can you say 4th Gen 4runner upper rear shock mount?) that sockets won't go and get bolts/nuts off fast without having to constantly reposition the wrench. I find myself using these wrenches more and more in places where I normally would have used a ratchet and socket. They are very strong, I've used them to remove and tighten things where I've really had to put some torque the fastener and they've held up well. At first I was concerned about the flex part being the weak link and breaking or spreading, but I haven't had any issues. The only problem I had was using the 19mm once when loosening a lug-nut (I was too lazy to get out my impact gun) and the ratcheting mechanism got "confused" and wouldn't ratchet, but a quick smack on concrete floor fixed it. It got the lug nut off and I haven't had any more problems. I know I've used some of the smaller size wrenches to torque things waaaay more than they should be, and wrenches haven't missed a beat.You do have to be a little careful when applying a lot of force to tighten/free a fastener to make sure that the head doesn't flex on you when you don't want it to or you may end up busting a knuckle (but hey, it hasn't been a productive weekend of wrench turning unless you have at least one bloody knuckle). There is a allen screw that serves as the flex pin that you can adjust to loosen/tighten the flex so you set it to what's comfortable for you.The "ridges" on one side of the wrench to help you feel if the wrench is tightening or loosening is just a marketing gimmick (at least in its current design). Yeah, they're there, but if you have gloves on you're not going to be able to feel them. And if you're like me, even if you could feel them, you're always going to give the wrench a quick turn to find out if it's tightening or loosening.....and you'll always have it backwards and have to flip it over!The plastic holder it comes in is nice and does a decent job of keeping the wrenches organized in your tool box, but I bought another wrench tray that stacks the wrenches a little closer together and doesn't "grip" on them to make getting them out just a little bit easier.So far, I'm very impressed with these wrenches. Seriously, if you don't own a set, buy some, they're that good, especially the flex head version. If you're on the fence, buy a smaller set and see how you like them and I have no doubt you'll be buying the larger sets in both SAE and Metric just like I did!