Build three remarkable machines: a ballista (an enormous crossbow), a bombard (an early form of the Cannon) and a mighty catapult. Send projectiles up to 15 feet! Each model is fully functional; the kit comes with 15 projectiles plus 18 paper targets. Everything you need to assemble each model in 1-3 hours: laser-cut wooden components, rubber bands, sandpaper and clear, simple instructions. No special tools necessary. Great for kids and adults, This kit is the perfect STEM school project or an office game. 100% satisfaction guaranteed. For 129 years, NATIONAL GEOGRAPHIC has been a brand you can trust for scientific and educational excellence.