The part that enters the body is Surgical Steel - the other parts are Aloy material. The aloy part may darken depending on use. (Chemical substances such as water, sweat and perfume can accelerate the darkening time.) Since it is surgical steel, it does not cause allergies on the part that enters the body. Since the other parts are jewelery material, do not use it if you are allergic to jewellery. Dimensions Height 2-4 cm. big ball size: 8 mm. small ball size: 5 mm. Bar thickness: 1-4 mm. Piercings cannot be returned once the package is opened for hygiene reasons.