Vluv sitting ball series. Minimalistic yet high-quality aids for healthy, active sitting: Kristof Hock independently markets this globally emerging design by giving the ordinary, widely secured PVC air ball a new and highly livable cover. Despite its outer layer, the inner PVC ball can be adjusted to the desired sitting firmness using a standard air pump, either by deflation or inflation. Additionally, a handy handle facilitates transport, while an integrated bottom ring effectively prevents the ball from rolling away. Vluv Veel sitting ball. The custom-made cover is made of soft yet durable synthetic leather that promotes warm and breathable active sitting. The smooth cover can be removed via a zipper.