After almost 3 years of relentless research and development in the tireless pursuit of perfection, the Classic Heavy Bag has been engineered to address the long-standing challenges that have plagued traditional boxing bags for decades. By using an internal circular steel frame that mounts at the top, sagging, inconsistent rebounds and durability are fears of the past. Made from a custom-developed 1/8" microfiber that uses a polyurethane substrate to form a three-dimensional mesh structure, our bags will outlast any leather or PVC boxing bag on the market. 6 reinforced straps and steel rivets secure the body of the bag to the internal steel top structure which are then secured to heavy-duty steel buckles to ensure longevity. Custom developed 3/8" impact foam sits behind the microfiber and is then machine filled with blended fabric to ensure a dynamic interaction of rebound and resistance.