Counter to logic, Sram did the seemingly impossible. They made a lighter crankset by increasing its size and made it not only lighter, but also stiffer by removing material.
The Sram Red Exogram crankset features an entirely hollow carbon arm structure. There are no alloy beams or reinforcements like on the old Red cranks. They also use the crankarm as a spider-arm, eliminating the need for a 5-arm spider. This allows the cranks to be much lighter. Bolting the chainring to the crankarm in this way also stiffens the chainrings under load, decreasing flex under hard shifting. Further increasing stiffness is the new X-Glide R chainrings. X-Glide Road chainrings are thicker than previous models so they are stiffer, and have revamped shift timing pins and ramps so they work seamlessly with the Yaw Front Derailleur.
Sram claims the Red Exogram crankset is the stiffest crank they've ever made. It's super light weight and smooth shifting is icing on the cake.