There was a thread a couple weeks ago about how
to change a ceiling box to accomodate an LED recessed
light that you can just mount to a round 4" ceiling box.
Poster had a problem, because there was a clearance
problem with his particular existing box.
Anyhow, I was at HD this AM and as I was walking by,
they had that fixture
on display at the end of the aisle. They showed it
mounted to one of those 4" ceiling boxes with a metal
bar so that you can position the box between joists
in the ceiling. As we already figured out, it's not
really a true recessed light. It sticks out about
2" from the ceiling. But it does mount directly to
the 4" box. I couldn't see the backside, how far in to
the box it goes, etc, because other than the display one
they didn't have any to sell so I could take a look.
But for $25 it looks like a good solution for certain
spots, like over the kitchen sink, which is where the
OP was gonna put his.