well... I guess I should get on the ball and weigh in here....

LOL
IF your lights are sitting right down on or near the screen and your chams hang close to the fixtures .... say between 6" - say.... 18" , you can go with the 6% and that would be just PERFECT.
Hoj is right...
THE T5 12% HO Arcadias are "KER-POW" in UV out-put...
And the 12% T8's (reg out-put) have some kick, too.
So to be safe:
IF you are using ANY 10% to 12% bulbs, I highly recommend investing in a Solarmeter.
Yep.. Solarmeters are expensive.
BUT if you have cages where YOU CAN HANG AND ADJUST THE LIGHT DISTANCE...
You can use a 12% HO fixture and Arcadia HO T5 12% and hang it up over the whole enclosure around 18" - 24" and measure the UV to the basking spot(s).
If it is good, say 30 - 60 microwatts per centimeter square to a basking spot(s), go with it. Or adjust as needed.
(More or less
tailored to your species of cham... remember.

)
Then simply measure every 2 mo. or so and move the fixture down 3 or 4 inches over a period of 12 months to a year and MORE.
A set up like that I guarantee will pay for itself.
(Instead of tossing those Exo teara bulbs out every 6 mo.)
So, as a recap:
If there is no hanging room to suspend a fixture and adjust, and if you do not have a Solarmeter (yet

) to double check...
you still would be perfectly fine using the 6% bulb.
Arcadias ARE the finest reptile bulbs in the world.
Yes... some others are good, too. (Full disclosure: I do sell Rept Sun too and they are OK.)
I say this:
I HAD to get them to sell.
I have been doing herps since the late 70's. (yep... I am old as dirt)
And I knew of the Arcadia reputation in UK and Europe.
But I
pestered (LOL

) Arcadia for 6 months to start shipping me those bulbs so LightYourReptiles.com could start making Arcadia bulbs available in North America.
Because I wanted to offer what I believe is truly the best.
From one of the best companies in the pet industry, Arcadia.
I am glad my friends at Arcadia went along with 'ol Todd here.
They are also starting to convert over some of their 220v European lighting products to work in US and Canada on 110v 60Hz.
There will be more cool quality stuff on the way.
http://www.arcadia-uk.info/product.php?mid=12&lan=en&sub=&id=4&lan=en
Cheers, and feel free to e-mail with any questions.
I HAVE A SPEC SHEET OF SOLARMETER READINGS OF THE ARCADIA T5 BULBS AVAILABLE FOR ANYONE WHO E-MAILS ME. Taken with and without screening. oh yea.

Sincerely,
Todd
[email protected]