This detachable magazine is constructed of steel with a black oxide finish and is compatible with your Ruger Security9.This model has a 10-round capacity. Ruger 90638 Security9 9mm Luger 10 rd Steel Black Oxide Finish Ruger 90638 Security9 9mm Luger 10 rd Steel Black Oxide Finish Ruger 90638 Security9 9mm Luger 10 rd Steel Black Oxide Finish