It is a flat fiberglass plate in various thicknesses. It is the same stuff that is used between the copper in a PC board like that of a computers motherboard. I am using it for the hinges and horns for a B-25. I started making the control arms for the tail and found that the sheet I got is too thick for control arms there, and the 4-40 ball links are too large as well. May need to order a .060 sheet for those instead. The .125 sheet I got is perfect for the hinges though.