Anal Speculum
Strictly speaking, this is a medical equipment. Speculums are more commonly used for vaginal inspections by gynecologists. The speculum is used to widen the opening in order to insert an instrument or otherwise just see what is inside. The same is true of the anal speculum. It is used to open up the sphincter ani. What the partners do afterwards is up to them. It seems that this is not strictly for S&M play.
