What is T5VHO vs T5HO?

[banditpowdercoat]

I'm really curious as to how you can say T5's last 2+ years with no appreciable PAR loss when many have tested, all independently, I may add. And those tests say that after 10 month's, T5's can loose 40% or more of their PAR. My bulbs are a year old, 12 hrs a day on time. And I notice a diminish in light output. I can look at the lights when on now. No way I could look at them when they were new.