Our filler bags do NOT leak. They have been proven so by gyms, boxes, pro and college teams over the years. They are of an original design that allows ALL of the sand load of the outer bag to be held inside ONE filler bag. To change weight, just add or remove sand. Using only one filler bag per outer bag gives a tremendous advantage to the instability of the whole experience. The sand load of the filler bag shifts as a whole with the outer bag. This gives you the best sandbag training experience!
Photo above of our "Snake" bag in action at a CrossFit Games in Kansas City KS. Our filler bags are the same constructon but a different shape.
Above is a screenshot of an emailed review of one of our filler bags.