Never tried a butt plug? Start here. Slim and flexible; Curved for prostate pleasure and fun for any body; Made of non-porous silicone – easy to clean!. The Rumpy smooth butt plug from Doc Johnson; Firm-yet-flexible material offers a cushioning sensation; Realistic tip with ridged head for extra stimulation. A butt plug is a sex toy that is designed to be inserted into the rectum for sexual pleasure. Some plugs are designed (long, flexible and curved) to penetrate the sigmoid colon. Butt plugs are made of a variety of materials, the most common.