There is a elastic band inside the material of the cuff, it's very unobtrusive and works well. It's nice not to have to think about or mess with the cuffs. It makes layering easier and not having velcro means it won't attract gunk onto your cuff.
Instead of velcro strips, there are elastic bands that reduce too much air circulation but still allows some circulation. About 10% of circumference of the sleeve is still open with no layers. With a long sleeve base layer it will be completely closed to circulation.