I purchased this at Akachan Honpo about three years ago. The included breast shield is only 21mm (small size). This has never been used. Although I bought it a while ago, I only used it for a total of about a month, and it's in very clean condition overall. The instruction manual is included, but the original box is not. This is an older generation model, so I'm offering it at a lower price. ※This is a bit embarrassing, but I hope it helps. I usually wear an E cup, and my nipples are on the larger side, so a 24mm (regular size) was the right fit for me. The 21mm is a bit small, so please be aware of this when purchasing.