Boxing Spider Bags

What is a spider bag in boxing?

The spider bags are leather balls with air filled sacs connected to four corner posts via elastic bands. Spider bags capture the feeling of a double end bag, while also forcing the boxer to practice defensive rolls when moving around the ring. The spider bag presently is the only training device or technique that has the unique ability to work rolls with their normal punch combinations as well as footwork, and because of this it has been hailed in high regard. However, because the spiderbag requires a ring or four other posts for set up, it can be complicated to find the space.