This small, light ball caster uses a 3/8" diameter plastic ball. The height of the assembled kit ranges from 0.4" to 0.6". This ball caster kit includes a black ABS housing, a 3/8" diameter plastic ball, two spacers (1/16" and 1/8" thick), and two #2 screw sets. The total height of the ball caster, 0.4", can be increased to about 0.6" using the included spacers. The two included #2 screws can be used to mount the ball caster to your chassis (the distance between the screw holes is 0.53"). Note that our ball casters are designed for small robots; they are not intended to bear more than a few pounds. With more weight than this, friction between the ball and the housing will probably keep it from rolling well. Ball Caster Comparison Table Pololu ball caster ball diameter height with no spacers distance between screw holes weight with no spacers or screws 3/8" plastic-ball 0.40" 0.53" 0.03 oz 3/8" metal-ball 0.40" 0.53" 0.14 oz 1/2" plastic-ball 0.53" 0.58" 0.07 oz 1/2" metal-ball 0.53" 0.58" 0.32 oz 3/4" plastic-ball 0.91" 0.24" 0.25 oz 3/4" metal-ball 0.83" 0.61" 1.05 oz 1" plastic-ball with rollers 1.10" 0.48" 0.58 oz
