I often use different sizes of diamond bits depending on the job and I really only needed 1 1/8" and 1 1/2" and this set had and these and others. I was a little skeptical at first because of the cheap price, but decided the good reviews were enough to give it a try. I've only used these two sizes from the set a few times so far but I can say from experience these bits will last a long time so having all the other sizes available is a big plus as I use other sizes. The biggest piece of advice I would give to those who have never used diamond hollow drills without a guide is . Always start at an angle of about 45dg, always keep the water in the cutting zone, for which I use a sponge to control the amount of water and push only as needed, and finally cut at low to medium speed, not along high speed speed. Also, I always wash my beats right after so they don't build up on the material. Great beats great price would definitely recommend