I've been using heat set inserts for a while, but I've always had to buy 100 of the size I needed, then reorder another 100 whenever I needed a single insert I didn't have. This kit is perfect, since it already comes with almost every size I could ever need. In fact, it already came in handy! My electric shaver had a M2 insert that broke off and fell into the sink drain while I was cleaning it, and replacement parts aren't available. I knew I could print a replacement piece to replace it, but I was concerned about the tiny threads holding in the plastic. But in this kit, there was a perfect size insert to fix the problem! Without it, I would have had to wait for shipping, check if it fits, and finally fix the shaver days later. I'm very happy with the selection in the kit, but I do wish it had M2.5 inserts instead of the variety of sizes within the range included. M2.5 is used in electronics very commonly, and I did have to order some to finish a Raspberry Pi case project. That being said, that is my only complaint. The inserts are high quality, and has already proven useful.