You'll see many carb stones on the market listed as .5 micron, 2 micron, 5 micron, etc. When our engineers were developing our carb stone we sampled many different vendors and then inspected those carb stones using an electron microscope. The results were very surprising. In our testing we were unable to find an actual .5 or 2 micron stone. Although all the stones we tested were listed at .5-5 micron they actually ranged from 5-200 micron. With that said we are extremely skeptical of any stone out there that lists .5 micron and would ask for test data to prove so. Attached are some of the SEM images from our testing showing the wide range of pore sizes. We can confidently say that our carb stone is 5 micron because, like all of our products, we test the crap out of them before bringing to market!