The Zoo Med fixtures are my least favorite of all that I own but they do work well enough most of the time to run a K6500. I just bought a set of 6 off of Amazon. I have some longer ones from Light your Reptiles. They are probably superior to the others but so far I can't tell the difference.
I try to buy dual bulb fixtures designed for fish tanks and put my UVB and plant light in those. I only prefer these because they don't take up as much space on the top of the cage as 2 of the Zoo Med.