Will Air Vent specify gutter size?

No.

Air Vent has never specified the gutter size for use with its product and will not do so with The Edge Vent because of the infinite variables that are structure specific. Obviously, the drip edge of the shingles can be as much as 1-1/4" further from the fascia board compared to shingle installations without The Edge Vent. Therefore, narrow profiled gutters that have long runs and significant elevation drops could present some issues. Compatibility of The Edge Vent with existing or new gutter systems will need to be investigated for each specific structure by the installer.