Review title is Caused stiff, cracking jaw [SEP] I originally was attracted to the thought of tightening my jaw muscles/chin area.  However, after using for a couple days my jaw was cracking/sore.  I would be hesitant to use this type of jaw exerciser.  It is easy to clean.  It may have been a bit large for my small mouth.  But it was a pretty stiff silicone which required a good amount of force to compress.