Babolat RPM Blast 1.25
Nadal's long-time string of choice, and the one string in this batch with a full set of published durability figures: 12% tension loss at 24 hours and a roughly 15-hour typical restring interval.
What the sources agree on
The octagonal cross-section is a real, measurable geometric difference from the round profile most strings use, and an octagonal shape is the established mechanism behind extra 'bite' on the ball at contact — sharper edges grip the ball fractionally longer before it releases, the most commonly cited reason this string tests as spin-friendly even among other polys. The published 12% tension loss at 24 hours is a genuinely useful, comparable number precisely because most other listings in our catalogue don't have one yet.
Where they disagree
A 15-hour typical restring interval is Babolat's own guidance rather than a figure we've reproduced on our own stringing machine, and 'typical' inevitably varies by string tension, playing frequency and how hard a given player hits — we'd treat it as a reasonable starting estimate rather than a guarantee for any specific player's racquet.