I have been in several over the years and only one was a great master mind.  What I noticed is even when we were told the mastermind group would be peer and the person owning the company would only let selective people in.  I found they actually let anyone in.  One example I am a very seasoned business owner in and found too many people that were new to the business were in the group.  To me someone who didn't have any experience was not a peer match for me.  Also, I had to start asking my self why did I really want to join the group?  Hope this helped...Best!