I don't think that step up is safe for use. Any artificial practice for height and weight growth might be bring some negative effects. Therefore its better to deal with height problems through natural solutions such as; exercise and cardio workouts.
Your height is determined by genetics. Don't be scammed by someone selling powders, pills or potions to make you taller. If you are having a real medical issue with growth, go to a real doctor for a real diagnosis and treatment.