How can I use them to supply my grip at deadlift or pull-ups?
They are very different than https://www.decathlon.fr/p/sangle-de-tirage-musculation-souleve-de-terre-deadlift-traction/_/R-p-158597
Did I buy the good product?...
Edit:
OH NO this is not the good product!!! What I've bought is: https://www.decathlon.fr/p/bandes-de-renfort-proteges-poignets-gris-musculation-serrage-velcro/_/R-p-304125?mc=8517598&c=GRIS NOOOOOOOOOOOOOOO NO NO NO !!!!!!!!!!!!!
I don't know if it's useful!!!!!
It looks like you wanted to buy wrist straps and instead bought wrist wraps. At least, those are the English terms I'm familiar with and they still get misused.
It's still a useful product. Wrist wraps are used to keep your wrist from bending during pressing movements: exercises like bench press or overhead press. Some lifters use them during squats to keep their wrists straight too. You slip your thumb through that small ring, wrap it around your wrist, and then velcro it closed. You can leave the ring around your thumb on or off based on your preference.
Unfortunately, it won't have much effect on your grip for deadlift or pull-ups.
