The cardstock poster board looks to be 1/16 inch thick and the styrofoam board looks to be just under 1/4 inch thick. This can all be bought at hobby lobby or equivalent arts and crafts store. What I would suggest, since the reach pistol is my next project, is to start with 4 pieces of foam board stacked and glued together as the main body. Elmers extra tacky glue is perfect. Once the main body is together and dried, use the thinner poster board for all the outer detail pieces. If you are using the sliced pistol file you'll know what I mean. The main body, upper module and lower module can all be started with the foam board stacked, then finished with the thinner board.