Natural Animal Solutions (NAS) Ultra Magnesium Gel Muscle and Joint Care for Horses & Greyhounds is a triple-action muscle relaxation gel with Arnica. It is a clinical grade cold therapy gel that promotes muscle relaxation and support before and after exercise. It provides under saddle muscle care and relief from tired muscles, over exertion, fatigue, etc. The gel is formulated using magnesium, menthol, camphor and arnica which promote healthy muscle support.