AB ringflash. Although I'm not a big fan of AB construction and industrial design, I must say this flash works beautifully, and is right on the money for specifications. The electronics are great, recycling is 100% as specified, and official spec is a t=0.5 1/2000th. Divide by 3 and you get a realistic 1/666th. Paul C Buff makes a point of giving most of the recent models specifications in t=0.5 and t=0.1. One who has done his homeworks.