Brit: Instead of using a round host bar like traditional carbides a shaper bar uses almost an H pattern. It allows your carbide to work well on ice, host bar on hard snow and keel on the ski for all the snow! Only carbides I will spend my money on!
With the USI you can make them as aggressive or forgiving as you like (shaper plates, three mount locations and different stage fin kits). Just remember that any time you go to a different ski the rear suspension should be set up a bit different. This typically allows you to relieve your limiter strap setting and add a bit of preload to your front arm shock!