This magazine is compatible with your FN 509 Compact. It features a stainless steel body with a flat black finish, high visibility anti-tilt follower, extended floorplate, and mag sleeve. *Note- This mag will not work with FNS or FNX pistols.
Specifications:

Caliber	9mm Luger
Capacity	15rd
Finish	Flat Dark Earth
Model	509
Material	Steel
Type
Model Fit	509 Compact
Brand Fit	FN
Capacity	15