1 in.
support ballsCarbon steel housing(2) mounting holes, 7/32 in.Load capacity Ball Up: 110 poundsLoad capacity Ball Down: 44 poundsWeight: 1 poundHardware not includedCross Reference: Mathews B4500 1" Main Ball Transfer 1SP-B4500.diameter Steel main ballMain ball rotates on 1/8 in.