I have issues with my sacrum for a long time. It's very difficult to stretch that area and I have tried a few different product for this. This one was unique because it's very stiff. Not only that but it rocks side to side. The website states that you need to relax with it placed on your sacrum and rock side to side. What I found was that while rocking side to side it didn't quite get into my muscles deep enough. It's almost like it needed to be a little thinner and have higher sides. I am also usually very tender and even when using a foam roller I use a softer roller. This was a little too harsh for me. I wish it had been made of a more firm foam vs a hard plastic. I do think this could work for SOME people but it didn't quite work for me.