Inserts with internal threads: 12 pieces each M2, M2.5, M3 and M4  Metric Stainless Steel Inserts for wood, plastic, etc.  48 pieces in all. Many applications, such as using these inserts instead of blind nuts. You can drill a hole and not have to place the blind nut from underneath or behind your work-piece. Just screw in or epoxy the insert in place. No need to get underneath or behind the item your working on. An example would be to use inserts instead of blind nuts for your landing gear on radio control airplanes.