after looking at an rsp post in person, i would assume they are the same. the tube looks exactly the same compared to Epost frames. i just wanted to see if anyone has actually fitted the seat post into a seat mast frame.
Look now calls the Re-Post the "RSP" and sells two versions of it. One with normal setback and and RSP-5 with 5 cm TT style. In fact the current 586 RSP comes with the RSP post instead of the E-Post (no seat tube cutting required). The same RSP or Re-Post fits both 595 and 586 (but you lose the elastomers, which earlier E-Posts didn't have either).
E-Posts for 595 and 586 are completely interchangeable, too.
So are the mountain bike and TT aero posts. I've had R5 (576, 986) and R32 (596) on both 586 and 595 frames. So the Re-Post or RSP will work on all of these models, too.
The only aero post that I think won't fit is the one that is unique to the 496. But I've never tried it.
Hey, I'm not going bald... I'm getting more aero.
2007 Look 565 (Ultegra 6600, Ksyrium Elite); 2005 Felt B2 (2010 Rival/Red, Rolf Prima Vigor); 2009 Look 586 Pro Team (under constr. 2009 Force, Rolf Prima Elan); Trek 7200 (stock stuff); Yokota Yosemite (Deore LX, Wheelsmith, Rock Shox)