Lee offers ployester filters and resin ones.  I wonder how these comare to glass.  They offer glass but the home page does not have a link I could find on glass filter pricing.  I imagine it is a lot more than the plastic versions.

Thanks for the imput so far. This is quite helpful to me.  The info on distance from the lens for graduated nd filters is good to know.  This would seem to add some versatility.  Thanks again.      Tom.