There are a few differences between these two mats. First, the obvious difference is the thickness. Our Premium mats come in either an 8mm thickness or a 3/8" thickness. Our Premium Mats are vulcanized, which means they are non-porous, whereas our Extreme Mats are not. Our Extreme mats are not finished on the bottom and are not trued as well. This means, if you are installing these mats as a full floor, you will want to make sure that you install them in a brick pattern to minimize the imperfections of the flooring. Both are great for moderate weight lifting and will help protect your subfloor. Even though our Premium Mats are thinner, they are still just as durable or more durable due to the fact that they are vulcanized.