I wanted to share my experience with this bit and give some details that differ some from the other reviews posted here. I use this bit in a CNC router.Firstly, this is a metric bit. The shank is 6mm in diameter.This will NOT safely secure in a 1/4 inch collet. You must use a 6mm collet on your router or spindle.There are some bad reviews listed here complaining that the bit did not fit well in thier 1/4 inch collet, and that is the reason why!!The description states that it can be used for steel and brass, but I don't think that is accurate.The bit angles down to a .3mm tip and I doubt very seriously that the thin tip can withstand cutting into any type of metal.I use mine to cut wood, specifically hardwoods, and it performs beautifully.Though a word of caution, you can't push this bit hard due to the thin tip.It will break very easily, so your feed rate needs to be slow.I broke the first couple of bits that I bought, but once I found the proper feeds and speeds, I have not broken a bit in a very long time, and I have put several miles on it.It is very sharp and the geometry seems to match the product description, though admittedly I have no way of measuring it accurately.This has become my go-to bit for engraving fine detail, and it seems to be the only bit that I have found that possesses the shallow angle (15degree) as well as the small tip diameter.If you need a narrow bit for super fine detail, I don't think that you can get any better than this.