They become non-functional after a few uses
I've purchased these a couple of times and both times at least 2 of them did not functional or became non-functional after 2 or 3 uses.  I thought maybe they were just a defective batch so I purchased the product again and the same thing occured. They are crap. Do not buy.  You may only get 1 or 2 good ones out of the 4 pack.
Rating: 1 stars