Pros - With 12 balls/bag, there are lots of extra balls to replace ones that you can easily loose. I think this is the best product for self myofascial release on the market. The ball can get to tight areas that you can't get to with a foam roller. Saves money in the long run because you don't have to go to massage therapist, physical therapists, etc. as often.
Cons - May be too hard for beginners.
I would recommend beginners start with a tennis ball and/or a foam roller. I recommend this to anyone using a foam roller who wants to take it to the next level. Champion Sports Official Lacrosse Ball Set of 12