Proline makes 2 kinds of closed cell inserts. The black ones will make your tire shape more rounded with the hump in the middle like the Aka's. The blue ones are more squared to give your tire a more even contact patch. Both PL black and blue are stiffer than the new Red AKA's but softer than the original Black AKA inserts. That's the extent of my findings. I have not noticed softer or different shaped proline inserts in the same colors.