CBT-1 1/2" SS Flange Mounted Ball Transfer Unit 1-1/2" Main Ball Proudly made in the USA CBT-1 1/2" SS Flange Mounted Ball Transfer Unit, Main Ball is 1-1/2" Inch, 1-1/2" Main ball rotates on (90) 3/16" support balls, CBT-1 1/2" SS is a heavy duty ball transfer unit, capable of supporting as many as 250 pounds (per unit).