16-oz. non-skid polycarbonate tumblers. The Captain Series includes one each of Captain, First Mate, Galley Slave and Crew. These are double insulated tumblers meaning they're two tumblers in one. The air space in between the tumblers keeps hot drinks hotter longer and cold drinks colder longer. Plus, they have a non-skid ring to prevent sliding and most importantly, they have a flat bottom so they don't tip over when the boat heels. And, they're priced 30% less than the name brand. 4 per box.