Get a more stable seat with this set of 4 ball feet made from VIBRAM rubber. 

45mm: Compatible with Chair One, Chair One L, Chair Two, Chair One Mini, Speed Stool, and Chair Zero 

Height  1.75 in / 4.5 cm2.5 in / 6 cm

Width   1.75 in / 4.5 cm3 in / 6 cm

Weight  8 oz / 228 g9 oz / 251 g

Length  1.75 in / 4.5 cm10 in / 25 cm