Purchased three units to be used with a touch dimming transformer, plugged into a wall outlet.
NO instructions were included at all, not that installation was all too difficult so any reasonable do-it-yourselfer would be able to figure it out. Just surprised that there were simply none.
The retaining clips riveted to the cast aluminum housing are relatively large, meaning that for flush mount, the mounting hole has to be nearly the same size as the flange diameter. With the hole so large as compared to the housing, and only two retaining clips, I could see where there might be issues keeping the unit centered in the mounting hole. The housing is 2-1/8" diameter, and it looks like you'd be hard pressed to fit it well in a 2-1/4" diameter hole. The design looks to be better suited to use a surface mount housing versus flush mount.
The three clips that hold the glass lens/cover are held in place by the reflector. In one case, the reflector was not formed particularly well, so the clips were loose and did not retain the glass lens well. This unit required rework to function.
Ultimately, once installed, the units functioned well and are a simple disign, but the intallation, at least in my case, did require some creative rework.
This item was needed to replace one of twelve identical ten-year-old under-cabinet lights whose ceramic connector had failed. I was lucky to locate it through the Internet, and especially lucky that the person who took my order was willing to call the supplier to double check and correct an error in the specifications they had provided, so I could feel safe in placing my order. The price was a little high, I thought, for this small item, but I've no complaint -- it solved my problem!