The quintessential leather strap. Barenia leather from Haas tannery in France is widely used by Hermes, and Hermes doesn't just choose any leather to use. It only uses the best. This is the same Barenia that Apple uses for its Apple Watch strap, and Hermes for its Birkin bag.
Barenia leather is soft and supple, with just the right firmness. It has a very smooth surface, with just a tiny bit of gloss. Closer inspection can reveal the beautiful grain on this leather. It has moderate scratch resistance which means you don't need to baby the strap. Small scratches can be buffed out with just some slight rubbing. This also means that Barenia is able to develop a beautiful patina that results in a slight darkening of the leather with use.