This is the Sram Red eTap AXS Rear Derailleur. Designed for both 1x and 2x, the derailleur keeps the chain silent and secure thanks to the Orbit™ technology. The Orbit chain management technology uses a silicon fluid damper system that, unlike a friction clutch, adds no additional friction on the derailleur's spring when under slow/light motion. That means shifting and removing the wheel is easy, but the chain bounce and slap is reduced. Also, AXS technology allows you to customize your shifting to how you want it.