When BH introduced the Ultralight in in 2011, it ushered in the BB386EVO bottom bracket and a then-insanely light frame. Building up a 10.66lb complete bike didn’t hurt, either. As the years progressed, they introduced a more affordable and only slightly heavier Ultralight RC, which carries over unchanged for 2015.
But, the top of the line is taken over by the new Ultralight Evo. It has a new carbon layup that makes it even lighter. Last year it was 750g, for 2015 it’s averaging 690g. And it has no rider weight limit and comes with a limited lifetime warranty.
Beyond lightening up, they tweaked the frame to make it a bit more comfortable and improve clearance around the bottom bracket for power meter equipped cranksets.