Number of packages: 2*Muster ball mandibular training device Size: 3.5cm*1.8cm Material: Silicone Color: black, white, gray description: This can train one of the most important but still forgotten muscles in the jaw, the masseter muscle. This is suitable for all adults who want to reconcile, firm and strengthen the entire face to neck area. For anyone who wants a slimmer face or double chin reduction effect For athletes, it will improve the connection between the body and mind and strengthen the muscles. For men, it can help you get a unique male jaw and increase your metabolism through constant chewing exercises. For women, it can help tone and tighten the chin and activate all facial muscles, thereby making the appearance more youthful.