This ball caster kit includes a black ABS housing, a 1/2" diameter plastic ball, two spacers (1/16" and 1/8" thick), and two #2 screw sets. The total height of the ball caster, 0.53", can be increased to about 0.7" 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 0.58").
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.
			
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Comparison of Pololu ball casters
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			 Pololu ball caster ball diameter  | 
			
			 height with no spacers  | 
			
			 distance between screw holes  | 
			
			 weight with no spacers or screws  | 
		
| 
			 0.40"  | 
			
			 0.53"  | 
			
			 0.03 oz  | 
		|
| 
			 3/8" metal-ball  | 
			
			 0.40"  | 
			
			 0.53"  | 
			
			 0.14 oz  | 
		
| 
			 0.53"  | 
			
			 0.58"  | 
			
			 0.07 oz  | 
		|
| 
			 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  | 
			
			 1.10"  | 
			
			 0.70"  | 
			
			 0.36 oz  |