I filled it with sand and reached a weight of 22kg. The stated maximum weight of 35kg clearly assumes a heavier filling. The inner bags are very thin and I definitely recommend wrapping them in foil or putting them in a plastic bag. One of them started to tear around the stitching. The outer bag itself seems to be durable, only the zipper is not secured in any way (usually there is a Velcro over it). Just to be safe, I taped it. The strap fabric is quite rough and may scratch in the joint area during explosive movements (in some grips only). Given the price, however, it is a good product.