Most of the time, the recessed cans are sold separately from the trim. Where that typically differs is with vapor-tight lights that are sold. Sometimes vapor-proofing is required where explosive gases (no, not toilet/husband related) as might be found in a shop or a laboratory might be ignited by an arc or spark. If you go to Home Depot or Lowes, they sell cans. Various types. You'll want an air-tight can, one that's rated for insulation contact. You can buy the can size that you want and then get a trim ring to fit it, but typically you'll find a trim ring of a certain size and then buy the correctly sized can to fit the trim ring. Shower trim kits sold at HD usually have a glass lens to contain the bulb, as well as a "sticky" rubber gasket that gets pinched between the trim ring and the can when the spring-loaded ring is snapped into place. Those are good enough for a shower, but they're typically not good enough for a steam room. Vapor-tight for residential steam showers? Those lights have a gasket between the trim ring and the housing, and screws that hold them together to truly make it tight tight tight. They're usually quite a bit more expensive. Realize that some cans are "remodel" and some are "new work". Remodel is if you're going to cut a round hole in the drywall and insert the can into the hole. New work is if you have the ceiling gutted and you can see the joists. You install the can, then hang the drywall, then cut the hole out so the can can pop through. So, how to shop? Go to a store and find a shower trim kit that you like. It'll be a certain size, 4", 5", or maybe 6". Now find a can to fit it. Choose a new work or remodel can based upon the stage of your project. Make sure it's air tight and insulation contact rated. Inside the can is a sticker that shows the maximum wattage for various types of bulbs that can be used in that can. Don;t exceed the wattage. If you do, the can could overheat. IC-rated cans have a thermal cutoff that will cut off power if the can temp gets too high. Most cans are a standard depth. They make shorter cans for low-clearance situations too. At HD, the can may run you $10. The "wet" trim kit may be $20-40. Vapor-tight lights intended for steam rooms? They can be $75-$300. Confused? I am! Best, Mongo

The work plane of 30 inches (2.5ft), is the height above the floor where the footcandle and beam diameter measurements are taken. The column in the middle with the additional heights, refer to the height of the ceiling where the light is recessed. For an 8ft ceiling, you get a measurement of 37 fc and a beam diameter of 5 ft, when measured on a flat surface 2.5 ft above the floor. The answer to your question about the diameter of the light at eye level can be extrapolated depending on your ceiling height. However, I am not sure the answer is a relevant. This will only tell you whether you are getting direct downlight from the fixture on your head. Note also that the beam of light from the fixture is not entirely uniform. As the spec says, the intensity of the beam is only at max in 50% of the beam directly under the fixture. The intensity of the beam will diminish as you get to the edge of the beam diameter.

Recessed fixtures for slope ceilings are adjustable to allow the lamp to be aimed straight down. Standard recessed housings can use adjustable trims. Recessed fixtures made for slope ceilings have this adjustability inside the housings for a cleaner looking ceiling with less glare. With typical 6" housings the cylinder walls will be perpendicular to the ceiling if standard or approximately perpendicular to the floor if slope. You need to find out the brand and model of the housings to choose trims so you're going to need to get up there and read the label. Buy the trims from the company that made the housings to be ensure code compliance because they are ETL or UL listed that way.

If you don't mind doing a little research and if your electrician is cool with it you can save quite a bit by getting lighting materials online. The first electrician I got a quote from wanted to provide materials and they were not exactly what I wanted plus he wanted an arm and a leg for them. The electrician I went with had no problem with me providing the materials. For many of the materials the difference between online prices and local retailers is huge. The cans I decided to use were cheap Halo 6" cans. I ended up buying them from Lowes as there was no significant savings to be found online. However, the Cree LR6 LED fixtures I put in them were $78 each from an online retailer which was a big savings over anything local. For under/over cabinet lighting I bought CL2 low voltage wire online and he installed it. Good wire is incredibly cheap online and incredibly expensive locally. I also bought the transformer and led light strips online. He installed the transformer. I installed the strips which consisted of screwing in a few little clips and plugging them in. Again, big savings - especially if you know where to get the LED strips from. He wired boxes for my island pendants. I got the 12V fixtures online and hung them myself. Again, pretty easy to install. I ended up with nicer and more efficient materials at a much lower cost than I was first quoted.