KD Duo Ski TubeKD Duo Ski Tube The KD Duo is a 2 person partially covered ski tube. Heavy duty nylon wraps a 24 gauge PVC bladder for the construction, and the partial coverage gives two riders a contained seating area without fully enclosing the deck. Four soft grip handles run across the deck for both rider positions. A Boston valve makes inflation quick, the quick rope connector hooks up in seconds, and the design holds up to weekend use behind a boat or jetski.