The Felt IA seat post is compatible on all the Felt IA triathlon bikes. Includes saddle clamp and seat post mounting hardware.
Difflock Version: The Difflock seat post has a checkered textreme pattern and comes with traditional 3T Diflock saddle mounting hardware. Made with Felt's UHC Advanced carbon fiber. This is the post that came on most Felt IA models before 2019.
Veri-Lock Version: The Veri-lock seat post has a flat black color and offers infinite saddle tilt adjustment compared to the Difflock version. Made with Felt's Ultimate Textreme carbon fiber. This is the post that comes 2019+ model Felts IA's.
For help with installation go to page 75-80 of this document.