I purchased these on a recommendation of a friend, I was have issues with my rc tires on the rock track and my buddy suggested getting the 2 stage foams because they allow you to tune your tires by allowing you to change the firmness of the outter stage. I love these foams, I ended up getting the outter stage foams in soft, med and firm for different tracks. The night before I go to a track I change the outter stage to give me the best overall traction for that track. If I have not been to a particular track before, the night before the race I take out the outter stage and put the screws to my beadlocks in a ziplock bag. Once I get to the track and look it over, I chose the firmness I think will work the best and install them. By removing the foam the night before it saves time on race day, just don't lose or forget the screws or foams at home....it ruins your day...lol