I made the same fixture by buying the LED flat panel (designed for lay-in use) and bought the surface kit from Amazon.
Where to get new LED like this....
I posted a few months ago about our office updating light fixtures. They opted for new 2x2 & 2x4 LED panels. That was in the main office. The hallway has these fixtures that hang below the drop ceiling in order to be centered in the hallway. The electrician who did our work said he didn't know where to get any LED's like what is pictured here. Any suggestions?
