I've been using the 2Kg (each) version of these weights to build up arm strength due to accident. They're quite good quality and made with soft material. The velcro strap does seem unnecessarily long but, that's a better than being too short. :)
On my skinny arm it's not possible to get a tight fit so it does tend to slide when raising the arm. This is remedied by adding a folded hanky under the weight to 'bulk' out my wrist.
Be mindful of chaffing if doing a lot of leg/arm movement with these on.