ELEVN ALLOY PIVOTAL SEAT POST AERO 27.2MM No reviews at the moment Aero seat post. aluminum 6061 T6 anodized. Length: 250mm. Diameter: Aero 27.2mm. Designed to fit CHASE ACT 1.2 & 1.0 , Chase RSP 5.0, 4.0, & 3.0 (Expert & larger sizes) & ELEMENT (with aero seat tube) Use the Elevn Aero Seat Post Clamp in the same size 27.2, for the above frames