Stabilizer reduces rolling or pitching of moored or anchored boats by 50%. Weights (not included, but small mushroom anchors or salmon weights work well) are attached to the bottom of each string of Rocker Stoppers. The top of the Rocker Stopper attaches to the boom, whisker pole, outriggers, etc. with 3/8'' nylon rope (not included). Made of lightweight, high-impact, virtually indestructible styrene. Sold Each.