BDSM play parties are events in which BDSM practitioners and other similarly interested people meet in order to communicate, share experiences and knowledge, and to "play" in an erotic atmosphere. BDSM parties show similarities to ones in the dark culture, being based on a more or less strictly enforced dress code; often clothing made of latex, leather or vinyl/PVC, lycra and so on, emphasizing the body's shape and the primary and secondary sexual characteristic. The requirement for such dress codes differ. While some events have none, others have a policy in order to create a more coherent atmosphere and to prevent outsiders from taking part.