The AirFlap44 is specifically designed to connect a 4 inch hose coming from your Glowforge to the AC Infinity Cloudline 4" Fan. It includes a built-in butterfly valve, thereby serving as both an adapter and air-flow shut-off point when fan is not in use, to protect your Glowforge from outside cool air and moisture.
(If you own a different fan with slightly different dimensions, please request a quote by emailing us at 3DProdigies@gmail.com, provide your desired dimensions, and leave a name and phone number so we may contact you.)