This edition of Allure Ⅳ is a vibrating anal plug in smooth, rounded, non-porous silicone. A flexible loop at the base keeps it from slipping all the way in and gives you a hold for removal. The part that goes inside is much shorter than its full length. Vibration inside the anus often feels deeper and more spread out.
Use far more water-based lube than you expect, and add more as you go. Rest the rounded tip against the anus and hold still until the inner muscle relaxes on its own, then move in slowly; stop if it hurts. Keep the clitoris involved too, by hand or with a partner. Wash it well before it goes anywhere near the vagina.