Yes, the size can be adjusted on the bracket. Volume can only be adjusted at the source (e.g. TV, computer). It has a long cable, therefore suitable for televisions at some distance from the seat.

You can buy it directly from Sennheiser: https://ch.sennheiser-hearing.com/products/ear-pads-hd-559 Or search "Sennheiser 572287" on international shops that ship in Switzerland such as Thomann.