Elevn Aero Seat Post ExtenderWarm up? Cool down? We're not sure either, but one thing is certain, the race world is in love with the extender posts and the Elevn Aero Seat Post Extender for the Chase ACT, RSP, and Element Frames allows you to raise your existing Aero seat post for post race cool down rides or when cruising down by the beach. Length: 495mm *Only compatible with Chase RSP, Element, A. C. T Carbon Frames with Aero Seat Tube.