Hi, what size are B4 ball stud?

[mattlynch]

Hi , could someone tell me the diameter in metric of the ball part of the ball studs used on the B4 buggy? , i am asking because i would like to use the rpm ball cups which only seam to be made for the B4/T4 ,, with m3 threaded ball studs on my all metric X-pro, thanks for any help folks.