I was disappointed with this reflex hammer. You may think that all reflex hammers are of equal quality and cause contractions, but they are not. This is one of the cheapest plastic cases. Some reflexes can still be triggered with it, others are more difficult. Also if you are testing a reflex if you have to put your thumb on a tendon, the hard plastic will hurt after 2-3 tries. Better buy another reflex hammer in the $15-$20 range, you won't regret it.