I've been using Revgear heavy bags in my gym, both the 4 ft boxing and 6 ft Thai, for nearly 20 years, and they are by far the best wearing and best feeling bags I've worked on. Anyone who's hit a bag knows how most bags soon get soft on top and rock hard at the bottom as the filling begins to settle - unsatisfying up top and likely to cause hand injuries below. Over the years I've used these bags, and this is in a busy gym in which the majority of our work is bag work, they have consistently retained their shape and just the right level of give and rebound for years. Also, if you need a heavier 4 ft bag, you can have one custom made, as I've had several made over the years for my gym. And not only are they great bags, but they're by far the best deal. As a company in general, Revgear has always shown itself to be exceptionally gym-friendly and gym-oriented. They stand behind their products and make a good product to stand behind. I cannot recommend Revgear and their heavy bags highly enough.