If the Opal One Seat had a baby brother, this would be him.

The Euroshowers Opal WELL Seat is designed for the slightly smaller oval-shaped pan.  It  accommodates a pan width of 350mm and it's adjustable chrome finish hinges reach a variable length of 382-432mm.

Made of Duroplast, the Opal WELL is soft closing and features a 2 button quick release for easy removal and cleaning.  Suitable for top and bottom fix pans with both sets of fittings included.

https://www.replacementtoiletseats.co.uk/ourshop/prod_6768697-Euroshowers-Opal-WELL-Soft-Close-White-Duroplast-Toilet-Seat.html