Don’t know what it’s called! (Penbeagle TR26)

Board used to clad my bathroom , white with a sort of tongue and groove effect. The large piece is approximately 4ft square and the smaller ones approximately 18 ins square. Also a piece of plasterboard approx 3ft x 18 ins. They’ve been stored in the shed and have got a bit mucky but as you can see I’ve given them a wipe and they are clean underneath . I’ll take them to the tip on Sunday if nobody wants them .