WOW ! lOOKS GREAT .Are these good for a screen, are they quite dense ?

'Karl Foerster' is dense but narrow. You would have to plant them very closely together to make a screen, which isn't really practical because of the expense. There are better grasses for screens, such as the various miscanthus cultivars. I like 'Karl Foerster' as a specimen plant where you need a 5 foot exclamation point. This one is planted at the end of the row in my vegetable garden, surrounded by Coreopsis verticillata 'Moonbeam' to provide a skirt of flowers. (The coreopsis has grown in much more thickly since this picture was taken 3 years ago.)