The Summer My Bath Seat (Aqua) has three extendable arms that fasten to the bathtub with suction cups. It doesn’t budge when kiddo is in there, but it’s a little bit hard to remove. This is a great thing to have when you plan to have more than one child, because kiddo will grow out of it quickly. We used it for about four months, from 6-9 months, after he had outgrown the Angel Care Bath Support, and then Lyons Cub was sitting in the big bathtub unsupported, just with very little water in it. Thus, it’s for the time baby cannot sit unassisted yet; in our case, that was from six to eight months.
It would make a good hand-me-down, if you have friends or family with infants. I can also imagine it’s suitable for babies with disabilities, to give them more freedom but prevent them from falling over. Lyons Cub had gross motor delay in the first months of his life due to his growth restriction, so for him, it was perfect. Parental supervision is required at all times, anyway, so it doesn’t add more safety, just more independence for the child who cannot sit up straight yet. Oh, and it exists in pink, too. So if you have twins, you can put one in each corner of the bathtub, facing each other 🙂