Ripstik is a specific brand name for a caster board. Caster boards are skateboards with only two wheels instead of the usual four. You propel yourself along by carving the board... see the many Youtube videos. Excellent practice for sports such as surfing or snowboarding. You can also pair it with a land paddle for carving and paddling practice. Excellent cardio workout! Check it out on Youtube too. You can buy the paddles online, or DIY one yourself. That's my paddle in the pictures, but it's not for sale. Still not edgy enough for you? Pair them with a wing and practice your wingfoiling on dry land. (Pssst... I have a wing for sale too.) Two different sizes... the small board is more nimble, the large one is more stable. Any questions, just ask.