They are the T-2 nylon, but in different diameter. Ko'olau had D'addario making these years before D'addario marketed them as uke strings though. I think the Ko'olau gauging makes more sense but some people like the T-2. The Mahana is pro arte in different gauge and Golds are their original still made by another string company in Argentina. Ko'olau never set out to be a string maker, but they needed strings for their ukes and were not satisfied with what was available. In the end, they care about making good instruments. They know everyone will have their own opinion on what sounds best with them. They settled on what they liked best.