The Step Original Aerobic Risers - Circuit Size Made in the United States from durable, recyclable high-density polyethylene. Fits only the Fitness Step Two original purple aerobic risers for use with The Step Aerobic Platform  Circuit Size Four nonskid feet on each riser prevent platform from sliding or moving during exercise Intensify workout difficulty by increasing platform height by 2 with additional risers Each riser measures 14.5 L x 9.5 W x 2 H  compatible with 25 L x 11 W x 4 H Circuit Platform