Hello Brad,
The opening size is not published. It is a Replacement for Minka Aire Traditional Concept Ceiling Fan Models: F593-ORB / F594-ORB. It will not fit any other fan. If you have a similar type of glass you are trying to replace on another fan, you must search by the brand and model number of the fan you own. More often than not, these types of globes are made for specific fans and are not interchangeable between brands and fan models.
Hope this helps,
Greg Tillotson
