Re: Help - Bell diameter size Bushnell 4200 3-12 FFP
If you are looking at the 3x12x44, the outside bell diameter should be 54mm.
The Midway USA catalog (hard copy version) is about the best resource for scope dimensions I have found. It gives objective diameter, length and weight.
Why they don't put that information on there website is a mystery to me as they clearly have the data.