I had that firmfeel one for a while, and ended up selling it at a swap meet. I just didn't like it, and don't think it is even in the neighborhood of the Flaming River part.
The ff piece has a fixed length, that just seemed to short for my application, and I have no idea why there would be any variation.
The FR piece has an extremely long shaft that slides down inside the u joint, in fact I cut some of it off. No worries on it ever coming apart. The quality of it made the $$ seem well worth it.
