Unfortunately the manufacturer does not specify the hole diameters, however this unit should work with the standard 5/8 stud, and standard extension arms. The unit is approximately 6 x 3 x 3 inches.
Hi Andrew, thanks for your response. Could you give me a little more detail. It looks like it has various size holes and I'd like to know what's the smallest and largest size rods it can hold. Also, the 3x3 dimension, is that the measurement of the handle or the diameter of the actual round grip head? Thanks.