leupold sunshade difference?

[SuperMagnum]

I had bought a sunshade for my leupold 4-12x40 AO with fine threads and it screwed in perfectly. However, recently I bought a 6-18x40 AOT and the sunshade won't screw into this scope, upon looking at the new scope, the threads were more coarse, not as fine as the 4-12 what's the deal? The sunshade is supposed to be compatible with all the x40 AO scopes. Could the AOT scopes have different threads than the AO line?