CASTER KIT PNEUMATIC 8IN/20.3CMHeres a detailed description of what an 8 inch 20. 3 cm pneumatic caster kit is how it works, typical parts & features, advantages and trade offs. Im using a real example as reference: 8 in. Black Rubber and Steel Pneumatic Swivel Plate Caster (and similar). means the wheel is air filled (like a bicycle or car tire), rather than being a solid rubber or plastic wheel. The air filled tire cushions impacts, absorbs shock, and provides smoother rolling on