Here is a 6-inch round canless LED downlight with a white trim from Lotus LED Lights, part number LE6R-5CCT-WH. The fixture is only about 0.5 inch thick, so it mounts directly under joists, ducts and pipes, in new construction or as a retrofit with no housing.

A selector gives you 2700K through 5000K in five steps, with about 910 to 1070 lumens at 14 watts and 90+ CRI. The driver comes pre-wired in a connection box and the trim snaps into the hole on built-in spring clips.

• Manufacturer part number: LE6R-5CCT-WH
• 14W, 120V input, 5CCT user-selectable: 2700K / 3000K / 3500K / 4000K / 5000K
• 910/970/1050/1070/1030 lumens at 2700K / 3000K / 3500K / 4000K / 5000K, 90+ CRI, 110° beam angle
• TRIAC dimmable with the included 120V driver; 0-10V driver available as an upgrade from the manufacturer
• Type IC rated and air-tight; rated for wet locations such as showers and soffits
• 6.875" outside diameter, 0.5" thick, 6.25" to 6.5" ceiling cut-out; about 1-1/2" of clearance above the ceiling for the driver
• cULus listed; 5 Years manufacturer warranty

Sold per fixture, driver included.