Level 1, Yellow. Each pad in the series of 5 Progressive Balance Pads has a different level of "give" and offers a different vestibular challenge. Yellow is the least unstable (easiest), and black is the most unstable (most challenging) surface. The Cando Instability pads are made from the same foam as the low impact aerobic pads. This combination of foam and geometric cut-out design yields comfort and functionality. Pads can also be used as core-strengthening vestibular seating cushions. All pads measure 20 inches in diameter.