4 in. Round Weatherproof Box with Five 1/2 in. or 3/4 in. Outlets

1.5 inches

an inch and a half. i picked it specifically for that depth.

6-32 screws are needed to attach the fixture mounting bracket to the box.

No, this electrical box does not mount to an existing, in the wall/recessed, electrical box. It is a surface mount box; note the "ear" mounting tabs on the edge of the box so it can be surface mounted on wood, etc. Usually, the electrical wire would be run through the center hole and clamped. I used the box under the eaves for floodlights, so I used a watertight connector on the wire to prevent any risk of water entering the box. Usually the cover (sold separately or as part of a light fixture) has a rubber gasket to fully seal it.

We've had 3 of these installed on our house siding for several years now for our flood lights and have had no problems at all with water seepage. Most of the lights come with a gasket to prevent water seepage between the fixture and where it attaches to this box, and we've had no water getting in along the back where the box attaches to the siding itself. For peace of mind if you're concerned, however, you could always get an inexpensive tube of clear outdoor caulk and lay down a strip along the top of the siding attachment area.

Silicone

Yes, just seal off the base of the fan to the box after using the foam seal.

The mounting bracket that comes with the Ring floodlight is to be used on the 4 inch mounting box. No need for any replacement of electrical boxes with the Ring

Any standard size wood screw will work to mount this box to a house. Unless it is into brick then you need to use an appropriate fastener. A #10 or larger wood screw at least 2+ inches should be fine. Try to find a stud as well. Mine was on the corner of the house so I knew there was a stud behind it. Put some silicone over the hole between the box and siding before you screw it in though to prevent water intrusion and rot over the years.