Exterior lighting: Is a round waterproof lampholder ACTUALLY compatible with a rectangular housing?

Question

I happened to be at Home Depot for something else, so I didn't get a good look at our exterior floodlights that need to be replaced (they're about 13 years old and don't work anymore). So I picked up two of these, just to have 'em in case they were a good fit:

http://www.amazon.com/dp/B00002N5FF/ref=asc_df_B00002N5FF1260862?smid=ATVPDKIKX0DER&tag=pg-894-10-20&linkCode=asn&creative=395093&creativeASIN=B00002N5FF

But when I came home I saw that the boxes on my house are rectangular and not round like the lights I bought. I was planning to just exchange them for the right kind, but then I noticed that in the description on that Amazon listing, it says they work for round OR rectangular waterproof housings! So... what gives? Can I actually expect to mount the round lights on the rectangular hole and have 'em work? Seems too good to be true.

Answer 1

The product description on Amazon is pulled directly from the manufacturer's data sheet (the link is an excerpt from a catalog, scroll down two pages for the light fixtures you bought), so I think you can trust it.

Another assurance that you'll be OK: I see from that catalog that the base of the light fixture is 4 1/8" in diameter, which is the same as the outside dimension of the diagonal of a single gang box (at least the one I picked out of my big box of electrical goodies :). When you open the packaging, you should see a rectangular pattern in the molding on the back where the electrical box will be mounted.