A double-ended boxing bag, also called a "crazy bag," "crazy ball" or "jitterbag," is a head-sized bag attached to a pair of bungee cords. The cords secure the bag between the floor and ceiling so it jerks for several seconds when hit. It's excellent practice for learning how to hit the head of an opponent in the ring, since the bag moves about as predictably as a trained boxer's noggin. When outfitting your home space for boxing practice, choosing the right size bag is an important step.
Assess Your Skill
Use double-ended bags at your boxing gym, or experience sparring against trained opponents to assess your skill level at throwing fast, accurate punches at a moving target. Ask your coach for help with this. If you're training on your own without a double-ended bag or partner, assume you're a beginner if you've trained regularly for less than a year, an intermediate boxer if you've trained for a year to three years, and an expert if you've had more than three years of boxing training.
Go online to a boxing or martial arts supply clearinghouse. These sites offer a wider variety of specialized boxing equipment, including double-ended bags, at a lower price than you'll find at your local sporting goods store. Local sports supply outfits will typically carry only the standard 9-inch bag.
Choose your bag's size according to your skill level. Use a 9-inch bag if you're a beginner, or an 8-inch or 7-inch bag if you're an intermediate boxer. Experts can use a 6-inch double-ended bag.
Resist the temptation to buy a smaller bag than you can handle in hopes of working your way up to it. Double-ended bags are one of the most frustrating pieces of boxing equipment available, and you're more likely to give up on a small bag than to put in the hours it takes to master it.