The device you use to hand the light.
Metal grate type thing.
In my perspective and this is just speculation, but here is my theory regarding cheeper 70lm/w type LEDS.
A CXB or Vero Bare can be at 10" at good Umol. Now the cheep COB run about half that umol at that distance, somy theory move then 50% closer and you should be hitting similar umol.
Thats my big problem. All ypou need to do is move the LEDS closer.
I will be testing this theory this year in a side by side in a 3 x 3 9 plants coco.
Would love to see this grow