The B+W filter is glass, like the excellent ND grads from B+W's parent company, Schneider Optics. The specs of the filter you link don't say, but the Schneider filters are 4mm thick, vs. the 2mm thickness of the resin filters from Lee, Singh-Ray, etc. If you go the glass filter route, you'll need the Lee 4mm side guides (for which reviews are mixed), not sure if you can use more than one filter at a time.