BycoreGlide™ 2X, 2 inch Extra Wide charcoal and firm, patent pending. The darker foam wears better than the white foam. Recommended for those who want deeper and firmer contacts and/or are larger people who may also be are taller. People with poor balance. Whose body movement challenges require extra surface area to support themselves. This 2" wider base may work better improved back flexibility or do not feel your abs and core engage during core exercises. You may also choose this if you want more balance support and only use this for your pelvis and hips and not the core exercises. Email our website if you have questions.