Burris don't to my limited knowledge make a fullfield 2 in a 30mm maintube scope. Humans have a pupil that on average expands to around 5mm in low light and 7mm in total darkness so all you need is 5mm exit pupil-anything bigger isn't needed and is uneccecary. For almost all normal hunting situations a 1" tube is all you need. To figure out how what the exit pupil on a scope,divide power into lens size mm. As in 8x into 40mm will have a 5mm exit pupil. Exit pupil in a scope is how big the scope image is.