Designed by a PE professional, these innovative 3-step series trainers are designed to maximize a student's success in the sport of volleyball by gradually progressing in 40-g increments to a heavier ball. Introduce students to the fundamentals with the lightest-weight trainer and as they become comfortable, replace it with the next trainer in the series, creating an effective training program. Bright colors indicate weight: Red is introductory, Yellow is intermediate, and Green is standard. Available in Official Size Series (8.25" dia) or Oversize Series (10" dia). Smooth, durable polyurethane cover. Includes usage instructions. Indoor use only.