The base of the bag will be empty upon delivery.
You can fill the base of the bag with either sand or water (or both) depending on what you're looking for in terms of weight and convenience.
We recommend going with sand for the best experience during your workouts.
Water is much more convenient, it will be easy to fill, to empty and to move around when needed. However the bag will be lighter with water (250 lbs) which means it will move during your workouts.
To get the best boxing experience, we recommend filling the bag with sand instead, that will make it much heavier (350 lbs).
For extra weight, water can be added to the sand, which brings the weight up to 450 lbs.