All PlayOnAir shoulder rests provide the playing comfort of an inflatable cushion that adjusts to body movements and changing posture while playing. Elastic straps are adjustable so your PlayOnAir can be placed in almost any position AND will fit any size violin or viola! No metal or sharp edges to damage your instrument, non-slip finish is soft and pliable. Blow-tube included allows you to inflate to just the right level of firmness.