I recently purchased a router bit for my industrial and scientific engraving needs. Based on my experience, it has worked well and saved me time during my projects .The bit fits comfortably with most machines, and the engraving on different materials is very precise. Plus I've used it for a few weeks now and haven't noticed any signs of wear and tear. The only downside I can see so far is that it only comes in two sizes..
These collet adapters are good quality at an affordable price. I use them so my router can use CNC bits and bits designed for use in a rotary tool when I'm engraving or carving. I think it's wise to buy a pack of these rather than a single adapter because they are so easy to find and so hard to find once they hit the store.