4 Fuel Cells of various sizes. In 1:24 scale the sizes (LxWxH) are 19x16x9.5mm 22x19x9.5mm 34x15x8.5mm and 22x19x15.5mm (tapered bottom) They are hollow and have drain holes in the bottom that can be filled relatively easily. Sold as a pack of four of one each. Design by Black Box STL