ORIGINAL: nksmfamjp
If it has little adjustment, it is bigger to allow more light through.
Not necessarily. I had 2 Leupold scopes, one being the VX-II 3-9 x 50 mm with the 1” tube that I sold and the other is my Euro 3-9 x 50 mm with the 30 mm tube that I still have and to be honest couldn’t see any difference between the two...