I bought a 7 gallon plastic Jerry can on ebay new for about$20. Fits great on eberlestock main frame with the steel shelf. Water is about 8.6lbs per gallon. Easy to add or subtract water. The water sloshes around quite a bit which test your balance on uneven ground. I like this as it's good prep for rough ground. If you don't like it you could use sand. Plus you can water you favorite fruit trees or berry patch and lighten the load on the way down. I do one long distance on level ground one day to work on endurance and do shorter steep ground the next day for cardio. It's easy to keep my target heart rate up on steep ground without the impact of running. Also builds leg and core strength.