Review on FREELICHT 12-Pack 4 Inch Slim LED Recessed Lighting with Junction Box - Ultra-Thin LED Downlight, 5000K Daylight, 9.5W=80W, 650LM, Dimmable Wafer Can-Killer Downlight - ETL Certified by Michael Barrett

I have used a 4 1/8 hole saw in some styles of Armstrong false ceilings. The fit was snug but with a little pressure they popped in the opening and fitted well. The spring clips I felt moved a bit from side to side during installation and that might be an issue but I was able to get them to work. Seems to hold tight after installation. The print wire connectors that came with the kit are ok, not the best quality I've used but they worked. I've found that the knockout holes in metal boxes don't accept all 1/2" knockout plastic retaining clips, some don't t press and bend the metal before inserting. Otherwise the installation went well, I threw away the spacer on the advice of the installer on YouTube. The headlights are bright and look great when installed. I don't know the possibility of dimming yet, but in general I'm satisfied with this money.