WPS SOLID WHITE 9" PANEL (225X1000mm) - 58553

This is a ~9" tall solid white panel - primarily used where the green category header magnets go at the top of a bay.  

One standpipe guide extension (61684) per standpipe will also be needed if you're converting a standard height bay to a "tall bay"

If you're looking for the same piece for a corner bay, order 58399 (you'll get one box, with two narrower panels that takes care of one corner bay).