Heavy-Duty Vinyl Bases - Official 15in Size Set of 3 heavy-duty vinyl baseball bases: 15in L x 15in Covered with 100 percent nylon-impregnated vinyl for water and weather-resistance Poly foam inner core allows for maximum shape retention and a great soft-landing cushion Inverted sewn corner seams for extra durability Designed to reduce sliding injuries / Not a substitute for proper sliding techniques