The apparatus may include a cavity for forming pre-cast concrete structures, such as concrete columns. A hinge joins the front holder to the rear holder. The method for recommending content includes creating a user profile according to a predetermined model based on a user’s reaction to the content, obtaining content features from one or more data sources, and creating a list of recommended contents according to a predetermined process based on the user profile and the content features. The ear tip is suitable for in-ear operation and has a deformable outer member.