i purchaced another set to save a buck but they were horrible. got these and first test i believed my indicator was broke. dead nuts spend the money once cry once and be happy every day after.Using this style end mill/cutting tool holder on my milling machine now instead of either 'standard' R8 collets or end mill holders (one size per unit). Makes changing between holder sizes a LOT easier/faster than otherwise. Unless you have a quick change system on your milling machine at least.Only time I remove the R8 part of this is when I need to use either the drill chuck, or go to the ER40 version for end mills with larger shank diameters (that goes up to 1" shank size).Like so many of the Accusize products, there are no instructions. The collet has to be installed into the cap before trying to screw the cap on otherwise, you can only catch about two threads as has been pointed out in other reviews. This would have been some handy information to know. I was in the process of sending mine back until I watched an unrelated video on YouTube.ER collets are an amazing thing for the home shop machinist. I love everything about the collets.Though these are imperial sizes, ER collets are springy enough that you can clamp down enough to cover any size in between.The case looks sharp but it is poorly made, like a cheap box a tween girl would use to carry her makeup in.The foam rubber insert is excellent, providing a way to store all of them--if I can find a way to keep the rest of the box from falling apart I'll be happy. You will be surprised at how compact this set is.Product comes in a really sturdy case, very high quality. Collets are exactly what I wanted.Excellent set of collets for the money. I’m a machinist of 20 years tooling up a home hobby shop that can’t afford to pay for the big name tools. I had been happy with some Accusize cutting tools previously purchased for the lathe, so I figured I’d give these a try. I’m very impressed with the quality and finish of these collets. I haven’t tried all the sizes yet, but what I have tried have been true, not adding any additional runout to my collet holders.Quality control on the product is not very good. The chuck seats well with no collet in it. When I placed a collet in to test fit, it only fought about 2 threads, which I knew could not be correct. On inspection I saw that the ID had not been finished out. There is a very off-center rough hole that a simple visual inspection before packaging would have caught.The material quality seems good and the collets were fine, so I chucked it up on the latch and finished building the tool...It works well now, but I shouldn’t have to machine my own tools when they arrive. I wasn’t looking for DIY. If you don’t have the tooling required to do this, you are going to have a useless chunk of metal. Caveat Emptor. Make sure you can finish machining the part on your own. I added before and after photos for your consideration.I considered sending it back, calling the company, complaining....Then I figured I’d leave an honest review and save others some potential trouble.i have a lot of general mechanical experience, but not a lot of milling or machining experience. but i've been obsessing with runout measurement on my new drilling/milling machine and the couple of these collets that i've used so far seem to be very true, probably less than .00025".Works great no issues