Plastic bottles make for great reactive targets! Each CTK Bottle Holder allows you to add a plastic bottle to the P3 Ultimate Target Stand. It accommodates most plastic bottle sizes (water bottles, 2 liters, milk jugs....). For an added reaction add water and food coloring to the bottles.Note Uses 1" x 2" furring strips from any lumber yard which normally measure 3/4" x 1-1/2".