@ epicfish. Naaa. I just bought one without (idiot me). And I have a Hagen hood without one... And other countries other lighting standards with pre-mades and sets -- but that w/g rule you can find everywhere, regardless.
@ wasserpest. In a nutshell if someone says he/she has 2w/g it can mean anything from low light to high light, depending on the bulb/reflector system?
It's really rough, this rule.
I.e. I'm told again and again my light's too low with its ca. 1,88 w/g. But in my estimation (by the plants I grow well) it's in reality in the higher medium light sector.
Anybody with the same (frustrating) experience?