Some variants of heavy bag are a Banana Bag used in Muay Thai, which is longer than a regular heavy bag and is used to train low kicks and knee strikes, and a slim line bag that is thinner than a heavy bag. Freestanding heavy bags are heavy bags mounted on a weighted pedestal rather than being hung from above. The base is typically filled with sand or water to give more stability to the bag and prevent it from moving around. While they serve the same purpose as hanging heavy bags, they can also be toppled over and used for ground-and-pound practice. Other variations on the standard heavy bag include horizontal suspension from both ends to practice uppercut punches, and non-cylindrical shapes. Freestanding reflex bags (freestanding speed bags) also exist. Uppercut bags began to appear towards the beginning of the 21st century. With so many different variations of bags and training equipment for boxing taking off, the uppercut bag was and is still a common sight in clubs and gyms. Designed for uppercut practice, jabbing, curl punching and quick bursts of high and low punching practice, it allows the fighter to punch at different lengths, different speeds and different forces compared to the standard average 4-foot straight PU (polyurethane) punching bags. Some types of uppercut bags: An angle bag a variant of uppercut bag used for training hooks and uppercuts; an uppercut horizontal punching tag, teardrop bag, body snatcher/wrecking ball bag or bowling pin bag are used for training knees and uppercuts. A wall bag is a type of bag that is attached to a wall and can be used for training hooks and uppercuts. Body-shaped training aids such as the modern "body opponent bag" are made primarily of synthetic materials, and punching bags are sometimes mounted on a weighted pedestal rather than hanging from above. These bags try to simulate a live opponent while providing an opportunity to practice vital area strikes which are generally unsafe to perform on a sparring partner. These are not considered punching bags in the strict sense, but modern versions of apparatus such as the wooden man apparatus of Chinese Wing Chun, the medieval quintain, and target dummies used in modern bayonet training. Large inflatable balloons with weighted bases are another kind of punching bag, often painted with a picture and sold as a children's toy. Safety precautions Heavy bags are typically filled