I use them while at camp. I have a single pole driven in the ground about 6' behind the stern instead of tossing anchors. They are fantastic, especially in high-traffic areas where the boat is in constant wave motion. The shock on the cleats and the pole are significantly reduced. Well worth the money in my opinion.
I have a Nitro 288 Sport Fish and Ski, 20'6" long. I bought the 6 footers that stretch to 9' maybe?