A ballast ball is a stability ball with 2.5 pounds of sand in it. You will use it to perform 4 of the exercises: Ballast Ball Sides, Ballast Ball Ups, Ballast Ball Chops, and Ballast Ball Pushes. I believe they are only made by Bosu. Get yours below.
A slam ball is a weighted medicine ball that doesn't bounce (or at least doesn't bounce much). You will use it, of course, for Ball Slams. A 10 pound ball is good for most people. I wouldn't go higher than 15. Get yours below.
You will use a kettle bell for the Kettle Bell Swing. The weight you use, obviously, depends on your size and strength. If you aren't sure, I would recommend a 20 pounder for a fit adult woman and a 40 for a man. Get yours below.
Battle ropes come in 1.5" and 2" diameters and lengths of 30 - 50 feet. There is a link below to buy one from Power Systems, or you could head to your local home improvement store.
A plyo box of some sort is needed for our one jump exercise (either Down / Ups or Up / Downs). The height of the platform doesn't matter too much. You just need to be able to comfortably jump onto it from the floor several times. You will find a link to an actual plyo box below, but I use an aerobics step and have also used a tire as well.
Coming soon: I am hoping to negotiate a deal for a "kit" with everything you need for the Power Circuit Workout.