T5 really need individual parabolic reflectors to give you the full output. The reflector (from my prior readings) should be W shaped with the bulb in the bottom of that sharp upside down V.
From the comments on the link to those fixtures....
"Instead of having six independent and "individual" reflectors, Current USA has taken a different approach. The reflectors are formed from a single sheet of reflective material: starting at one edge and then bent/formed around each bulb. The reflectors are not curved or parabolic around each bulb, but rather angled (picture cutting a stop sign in half) to achieve the "individual" reflectors."
I have no idea how much this will affect the light output. Here are commnents from threads on another board about T5's.
"So a VHO or a PC or a T5HO all about the same output in lumens, but it's the reflector that distinguishes each bulb. VHO's parabolic reflector would have to be huge and the PC's can't use a parabolic reflector because it is doubled and can't be put at the focal but the T5's can and that is why they are said to be soo much better. "
"T5 setups get all their benefit from the reflectors. I will say that I did a lot of research about T5's on Reef Central. There is a member there that goes by the name Grim Reefer that has done a lot of research with a par meter on T5's. I don't remember the exact numbers but he said that the Icecap SLR reflectors provided about 20% more light than the Sunlight Tek SLS reflectors. That's free light in my book. "
HTH