The numbers given to the different series were used to indicate various pieces of information; the first digit represented the manufacturer, the following number being used as a 'type number', which would be followed by a break and addition numbers of identify the individual fighters. The main differences between the different series was in the power of Austro-Daimler engines used (185 hp in the early production aircraft, 200 or 210 hp in the mid-production, and 225 hp in the last ones). Other key areas of change included the positioning of the machine guns, as well as various structural alterations and refinements to the radiator.