Internal Thread Tops are available in a range of colours and styles featuring jewels and gems.... Internally threaded posts are sold separately. Internal threading is where the thread the screw bit is on the ball top and goes inside the post. When the top is tightened it sits flush against the end of the post, meaning there are no gaps for any build up of debris or bacteria. Internally threaded jewellery also has a smoother finish, making it shinier, more gentle for insertion, and the flat end of the post it won’t cause microscopic tears.