Great convenient item
Your review: Used these for first time on older building where we insulated attic areas and installed airflow vents in eves...
Used a 5" hole saw and strong drill (28volt Milwaukee cordless in my case) and went slow to drill for these at height of approx 25' in air. Fit well but also added heavy silicone bead around inside edge before popping into holes to give guaranteed long term fit & seal.
Pros: Great easy product with higher collar on inside so you can even terminate a flex duct or such with ample clamp room.