
Hope you can see they are 1" outside the thread. They don't even exceed 3/4" of the inside diameter of the hole. I don't know if this is a packaging error, a deliberate attempt to confuse, or I don't know anything about industry sizing. Home Depot sold the same package and it was 3/4". Since my box had different sized punch holes, I was able to use them, but be aware that if you only have a 3/4" punch hole, they will NOT fit. .

Waterproof ABS Electrical Junction Box Enclosure With IP65 Rating - Black 7.87 X 4.72 X 2.95 Inch (200 X 120 X 75Mm) By Zulkit
12 Review

Zulkit Waterproof Plastic Project Box ABS IP65 Electrical Junction Box Enclosure Black 6.22 X 3.54 X 2.36 Inch (158 X 90 X 60Mm)
12 Review

β‘οΈ RVGUARD 50 Amp Weatherproof Outdoor Electrical Power Outlet Box - Lockable RV/EV NEMA 14-50R Receptacle Panel, 125/250V, ETL Listed
9 Review

Zulkit Junction Box ABS Plastic Waterproof IP65 Electrical Boxes Hinged Shell Outdoor Universal Project Enclosure With Mounting Plate And Wall Brackets Grey 11.8X7.9X6.3 Inch(300X200X160Mm)
10 Review

Fulham WorkHorse WH2-120-C Adaptable Ballast - 2 Pack
3 Review

π‘ Electronic FL Ballast ICN-4P32-N (Formerly ICN-4P32-SC) for 3-4 F32T8 F40T8 F17T8 Lamps, 120V/277V Compatibility
5 Review

Robertson Worldwide ISL432T8HEMV AH 3P20160 120-277V 50-60Hz High Power Factor 4 F32T8 Linear Lamp Fluorescent eBallast
6 Review

π‘ Hydrofarm Quantum QT400 Dimmable Ballast for 400W Grow Lights
5 Review