It was the pros that first asked for a gabba thats not as hot as the gabba but warmer than the fawesome vest so castelli started from the gabba and made the back in nano light fabric the same fabric as their nano flex tights but without the brushed fleece inside this gives the piece a lot of breathability and keeps you from overheating inside they further lightened it up by using a lighter weight of windstopper a full 25 lighter than the one used on the gabba on the front you may think