Well designed but too brittle plastic

This cover protects the phone very well during a fall. But as I thought when I received it, the plastic is too "brittle".
I had to remove once the teléphone of the case and a small piece jumped while I was very careful.
And yesterday I made my phone fell from a chair (thus about 50cm height) and what I thought it happened, the protrusions are broken. I have to buy a bag.
So this case protects well but only once, not two.
There are a lot of progress to make on the plastics used.