These T5 5/8th inch diameter standard tubes have a halophosphate coating to give a standard performance. Typically we supply the following brands: Philips, Osram, Sylvania and General Electric GE. Lengths include 6 inch 4W, 9 inch 6W, 12 inch 8W and 21 inch 13W. We advise you to upgrade to a superior quality triphosphor tube where your needs require longer life, higher and better quality ligh output, improved colour rendering CRI Ra and better lumen maintenance.