Using the tension of wound string, my hand sized catapults can launch grape-sized objects over ten feet.
They are good for older kids who like to build and launch stuff. Adults should help younger children. There are a few small parts that could be choking hazards for very young kids. Also good for adults who want to wage inter-cubicle warfare. Looks good as a desk decoration and conversation piece.
Below is a video with instructions on putting the kit together:
This is what the box (which I also designed) looks like: