A:  I would use a ceiling fan metal box to hang a heavy chandelier.

A:  I am not sure.  It is only held up by the 2 nails.  I would suggest a ceiling fan box with stronger mounts, this way you could hang whatever you want.

A:  I would never use a plastic ceiling box to hold up a ceiling fan, and only trust a metal ceiling box, that is firmly secured to the house structure. If you have a plastic ceiling box in this location, then you should replace it with a (Home depot) Internet # 204845572 Model# 0110000. I believe that this could be an unsafe situation otherwise.

A:  This is for new work. If you have existing sheet rock then get an old work box with tabs and drill a 4" hole. You may need to cut the rock away a little bit to get the tabs in. This type of box will not hold a ceiling fan.

A:  here is a link to the product specks. https://images.homedepot-static.com/catalog/pdfImages/b2/b29ea821-0af2-4005-a01c-620432ad84e6.pdf it has the manufactures contact information in it so you would be able to ask them this question. since the plastic for the screw holes is made to be malleable it may not be made to accept a certain size screw and may be made to accept common screws used for assorted lighting fixtures and ceiling fans. I say this as if you look in one of the holes you will see it is not threaded.

A:  OK, so I see this question has been sent to me a few times now as of today. I have installed a lot of these over the years, some with light fixtures, some with ceiling fans, some with the ceramic basement utility light , light fixtures and some with block off plates I am not even sure if they even make any more. And I have also installed the metal version of this product they make. With that being said, I have never removed one of the screws that comes with the above mentioned products and measured its diameter and thread count. Now the metal version of this product is a little different being you would really need to get the right size screw as it is not malleable. verses this plastic product is, the screw holes are normally unthreaded and some screws are much easier to get to go in verses others are not, which would indicate that different product manufactures are sending different size screws with their products that are being mounted to boxs like these. with all of that being said, these are a light duty plastic round single gang box, they are not water proof and are not made to be and really can not be used in any " mission critical " applications. So no boats will sink, no planes will fall out of the sky and no buildings will explode or collapse due to using the wrong size screw. If any one really NEEDS to know exactly what size screw it is designed to be used with they should contact the manufacturer and ask them.

A:  Use machine screw type #8-32 thread, with pan head or round head. I chose 1? long one, it could be 3/4?. My picture shows 1? long one. Also strongly recommend to put screws before you nail the box. Screws are very tight because it cuts thread.

A:  8-32 are used in a ceilng box.

A:  TL;DR: Use a high quality 8-32 machine screw. I did some more research on this after posting, and managed to answer my own question in more detail. Thanks to Thomas & Betts and Greg for your responses! I found some online debates about what type of screws were appropriate, and war stories about run-ins with electrical inspectors, but I eventually found an Engineering Bulletin from NEMA (National Electrical Manufacturers Association) that addresses this specifically: Bulletin No. 109, Screw Attachments to Electrical Boxes - Guidelines for Screw Substitution, Approved Feb. 5, 2015. The short(er) version of that article is: * Use a high quality machine screw of the appropriate size and 32 threads per inch. * Never use drywall screws! * The screw bosses in plastic covers may crack or break if you use screws that are too large or with different threading, and temperature fluctuations may also cause the plastic to fail. * 6-32 and 8-32 are the most common screw sizes, but follow manufacturer instructions. * In the case of a metal box (though this one is plastic), it is important to have the correct threads (32 per inch) to make sufficient contact with the electrical box threads for electrical bonding between the box and a metallic cover plate or canopy on your light fixture, in addition to the threads providing mechanical security (i.e. your fixture doesn't fall off the wall). I also read elsewhere that a big reason drywall screws should be avoided is that they are not rated for shear strength, and can easily break off due to the cheap materials used to make them. Electrical code requires that you only use materials designed for their purpose, which drywall screws with no shear rating fail for this purpose. While the screw bosses on this fixture are the appropriate diameter for an 8-32 machine screw, they are NOT pre-threaded, so you likely have to use either an 8-32 tap to thread the plastic, or a bit of elbow grease to force the screw to thread into the plastic.

A:  Normally these are used for lighting and fans, so you may not be able to find a round cover for this box.

A:  Assuming this is a finished ceiling, I have used these: 5 in. Ceiling Blankup Canopy for 4 in. Box - White https://www.homedepot.com/p/100152838 They blend in as is or can be lightly sanded and painted to match the ceiling paint.