STOTT PILATES MERRITHEW Rotational Disk, Single (19 inch / 48.3 cm) Sturdy and versatile, Rotational Disks improve strength through rotation and add variety and fun while standing or sitting. 19-Inch diameter. Sold individually Non-skid surface Baltic Birch construction Also available in 10-Inch (sold as a pair) and 12-Inch (sold as a pair). Search ASIN B0002V8LA8 or B0002V8L58.