The shields I received does not fall apart like one user states. Stays together in one piece as it should.
The CPR shield will not block bullets but it will stop blow back and prevent throw up in your face from helping a non breather.
I have tested the "one way valve" and it works for the most part. It doesn't look like a one way valve since all you can see form the top is the filter. The only thing about it is that it may be a little difficult to get a good seal on the victims mouth because of the blow back vents.
The over all size of the vinyl sheet is 6.5" x 6.5". The bite blocker is a little over an inch that protrudes into the mouth.
I would say this relatively inexpensive and good thing to always have in your first aid kit.