NASCAR Convertible Division

The NASCAR Convertible Division was a division of convertible cars early in NASCAR's history, from 1956 until 1959, although the signature race for convertibles remained a Convertible Division race until 1962. Two remnants of the Convertible Division are still used in the NASCAR Cup Series today: the Duel at Daytona (one Daytona 500 qualifying race was reserved for convertibles) and the Goodyear 400 (started as a convertible race until the end of the division).

Source: Wikipedia — NASCAR Convertible Division (CC BY-SA 4.0)