The "Play on Air" shoulder rest is a kind of inflatable cushion that is mounted under the violin and feels very comfortable. The thickness can be varied by blowing more or less air into it. The following models are available:

• Model #1611 for 4/4 - 3/4 (viola) violin - Deluxe version;
• Model #1611J for 4/4 - 3/4 (viola) violin - Jumbo Deluxe version;
• Model #1613 for 4/4 - 1/2 (viola) violin - Standard version;
• Model #1614 for 3/4 - 1/16 violin - Junior version

An explanation is given in the following video clip: https://www.youtube.com/watch?v=JMoFy-VsD6E