Info: Various Replacement Parts for Ball Chair
Replacement or supplementary parts are available for a Ball Chair like the one initially pictured (sold separately; but likely no longer available here), including the ball itself, various types of wheels, and height extenders. Please see notes below for details.
For Aviva's Ball Chair (shown in main photo) can help take pressure off the spine, release muscle tension, correct posture, improve balance and strengthen the torso. This ball, which can be inflated up to ~52 cm (10.4 inches) in diameter (it fills using a needle valve on a pump (not included), and comes with a long stopper).
Apart from use with these chairs, these balls are also suitable as exercise/yoga balls.
Various Ball Chair Wheel Sets
The wheels pictured on the top of this nearby photo are standard, free-rolling wheels. The wheels below it are manually locking: depending on how the small tab is positioned, it either enables sliding/movement while seated, or it locks the wheels in place to keep the chair stationary (two locked wheels suffice to hold the chair in place).
The auto-locking wheels (not pictured) are the ones normally sold with the chair; they are weight-activated, to prevent rolling when you are seated, and the locks release when you get up, so the chair can be repositioned.
Ball Chair Height Extension Adjusters
Set of 4 chair leg height extenders recommended for taller users or those sitting at a slightly higher desk surface. These 5 cm extensions (pictured here) are for use with the Ball Chair formerly sold here at Aviva and will also fit the BalanceBall Chair from Gaiam.