Collo
The legs are 25mm but not standard exact sizings.
I bought 6 X 750 lengths of 25mm OD tubing to replace my short extending legs.
Rive legs are ever so slightly smaller than the tubing I bought, not sure which was the most accurate(25mm). Rive legs are not round but slightly shaped, this is what might have been the issue I had.
I was able to remove the extending part of my Rive legs quite easily and add them to the new legs, everything fitted perfectly.
The problem came when I tried to fit the new longer legs, they would not pass through the frame of my ST comp. I had to file out the holes enlarging them slightly. All the old stile full fittings were the same, in need of a filing and hole enlargement. Not a long job as not much enlargement needed.
For me well worth the effort, cost £30 and a couple of hours. A lot cheaper than buying 6 long Rive legs