Now I have use a tennis ball for my feet before , but the problem with using a tennis ball, they tend to wear down very quickly and I ended up having to replace them quite often. So having been using the Cratosfit Myofasical Release Lacrosse Massage balls, they are very sturdy and make my feet feel very good after using them. They are very durable for sure and like that they come in carrying case. I have also use this for my shoulders as well, it seems to relax my muscles as well. I have saw online that it can help get rid of shoulder pain, neck pain, upper and lower back pain, hip and glute pain and stiffness, leg and knee pain, calf pain, ankle stiffness, Sciatica, Muscle tension ,Cure kinks and cramps anywhere you feel minor pain and tightness.. I suggest maybe doing research on how to use them, I think that these products can really help. So I give the product high praise but think they need to include some type of instructions or pamphlet with the product for users who don't know how to use them. Again I received this product for free for my unbiased review and my review is solely my own.