Tower.....
It all depends on the tower you have and who it was made by. Most towers, except the wake edition made by Seadoo, has aftermarket wake towers. The outside diameter of the legs is 2" and the crossmembers are up to 2 and 3/8". So, without more specifics about your wake tower, I can only give you these generic sizes.
I have a feeling, these sizes are pretty standard in the industry though.