Dating back to pre-Buddhist times the Bun Bang Fai is held around the May full moon, and is based on the notion that launching bamboo rockets skyward will initiate the rainy season and bring much needed water to the country's rice fields. Traditionally, rockets are constructed out of bamboos and stuffed with gunpowder, but today, many different materials are used, including PVC or metal piping. These rockets come in variety of sizes starting from foot-long bottle rockets to an absurd nine meters in length. Some of the biggest rockets are packed up to 120 kg of gunpowder and balanced precariously on a launching tower made of bamboo scaffolding.