The hair ties that I got from Groupon are not as strong as the ones that I buy from normal stores like Wal Mart, but they do the job. They definitely break more easily but with so many at such a small cost, it doesn't matter to me as much.
I buy and use this product very often. I usually get it from a beauty supply or my pharmaceutical store. The ones o got from groupon were smaller and many of them popped right away, the rest stretched out after the first use.