The quests for the lightest disc rotor is quite debatable. The lightest that would come out includes a carbon version and/or an aluminum version (i.e. Scrubs) but I tend not to consider them as they are more of a technical show piece than a real life application. They have disadvantages that the little grams that you save may not be worth the cost and those disadvantages. So the quest is about the normal stainless steel rotors. For the longest time it was the Alligator Cirrus Model. But recently this Ashima Ai2 model came out and it is now the lightest product out there. Note that I have seen a different brand with the exact same look so I guess the Ashima manufacturer (or subcontractor) might be doing OEMs for other companies out there or vice-versa.