SRAM designed each version of their Direct-Mount Front Derailleur to work with specific frames. Spec 1 features a wider bolt plate than Spec 2 and 3. Please see the chart and diagrams below to see which Spec will work with your frame.

SRAM XX Direct-Mount Front Derailleur Compatibility Chart
SRAM Direct-Mount Front Derailleur Compatibility Chart

SRAM XX Direct-Mount Front Derailleur Spec 1 Diagram
SRAM Direct-Mount Front Derailleur Spec 1 Diagram

SRAM XX Direct-Mount Front Derailleur Spec 2 and 3 Diagram
SRAM Direct-Mount Front Derailleur Spec 2 and 3 Diagram

SRAM XX Direct-Mount Front Derailleur Overhead Diagram
SRAM Direct-Mount Front Derailleur Overhead Diagram