Chairs Ray Soft collection from the company Brunner with the base Four Feet Extensions roll (on wheels). In three versions: low medium and high back. The base is presented in three colors: aluminum black and white. Links to the manufacturer’s website / store:
Low back: https://www.brunner-group.com/en-DE/products/details/ray-soft_9618/A/ 
Medium back: https://www.brunner-group.com/en-DE/products/details/ray-soft_9628/A/ 
High back: https://www.brunner-group.com/en-DE/products/details/ray-soft_9638/A/  On the seat applied modifier TurboSmooth. For all models a sweep.