Extreme stretching (fisting)

Inserting an entire hand into the vagina or anus. This is highly advanced and requires tons of communication, slow preparation, and lots of lube. Some find the feeling of being so filled intensely erotic and emotionally powerful. It should only be done if really wanted, with patience, and knowing how to do it safely (e.g., forming a narrow hand shape, going very slowly, and being aware of signs of injury).