My ~10 year old Mac catalog shows a 1/2" round head flex 30-250 ft-lb TWF8250A.
Same vintage SO catalog only shows a 3/8 flex QD2FR75. QD is the series, 2 is 3/8", F is flex, R is ratchet and 75 is max torque. If a 1/2" flex exists in this series it'll be QD3FR150, 200 or 250. They also have a QT premium series in the same catalog.
My older 3/8" flex is a QJFR275. You might be able to guess a part # for that series the same way.