they arrived today and are just as advertised with 3/16" thick VERY HARD and stiff plastic, they are top shelf adapters and way better than the Metra or Scosche adapters but i give em a 10 for the difficulty factor in removing the 6 x 9 ring of plastic that surrounds the 5 x 7/6 x 8 portion of the pre-scored adapter, i would say it's pre-scored just over 1/3 of the way through, taking a knife and scoring the rest of the plastic out of the groove as they advertise and recommend is out of the question and most definitely highly dangerous, instead lay the adapter down on the edge of the work bench and use a hacksaw or ? to cut slots all the way around the adapter about 5 inches long on the straight edges and about an inch long around the corners and then take 2 pairs of pliers to bend and then break the excess plastic off the adapter, 1 pair to hold the adapter and 1 pair to break off the pieces. If you're mounting a component speaker into a 6 x 9 hole then no worries you don't have to trim the ring but for 5 x 7/6 x 8 applications prepare for some time consuming prep work.
Edit: Remove only the very outer ring for 5 x 7 applications, there's only a small area of plastic left after removing the outer ring and there's no need to remove that last bit of material between the inner and outer ring.