Sportsstuff 52-1140 Justa Tube - 40" JUSTA TUBE is not really just a tube! Sure it’s a black donut, but it’s a hypoallergenic black donut, much less likely to cause an allergic reaction than that old truck tube you used to use! The Schrader valve stem is shorter than a standard auto valve and has a tapered cap, so there’s no discomfort or scratching legs. It’s made of isobutylene isoprene synthetic rubber, an upgrade from a standard tire tube. It’s more resistant to heat, abrasion, ozone and sunlight. JUSTA TUBE provides year round fun and is easy to store! It’s a durable snow tube in winter. In summer, you’ll enjoy it as a durable river, lake, pool or ocean float.