It was the pros who first asked for something thats not as hot as the gabba but warmer than a perfetto 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 castell perfetto light 2 a lot of breathability and keeps you from overheating inside they further lightened it up by using a lighter weight of windstopper on the front