ok.. here is the quote from RC. the article about the 250W Iwasaki and the R rating is in the magazineit is actually the 2002 Marine & Fish Reef annual.
<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>This very topic was just covered in the 2002 edition of Marine Fish and Reef USA Magazine. Which indicates that the "R" designation denotes the new carbon resitor but also goes on to say the new resistor is responsible for a better light than before. Actual kelvin value on the 6500K bulb goes from 6535 to 7660 so the bulbs appear less yellow than before.
I use them and wasn't aware of the change in the bulb however the new does appear much more blue than the old. Good Luck
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