Two original black aerobic risers that are ONLY COMPATIBLE WITH THE HEALTH CLUB STEP Four nonskid feet on each riser prevent platform from sliding or moving during exercise Made in the United States from durable, recyclable high-density polyethylene Intensify workout difficulty by increasing platform height by 2 with additional risers Each riser measures 16 L x 16 W x 2 H These risers are ONLY compatible with the 40 L x 14 W x 4 H Health Club Platform ONLY. They are NOT COMPATIBLE WITH CIRCUIT SIZE STEP PLATFORMS