SCHOTT filter glass product range - Our filter glasses are classified into the following groups:   UG Black and blue glasses, UV transmitting   BG Blue, blue-green, and multiband glasses   VG Green glass   GG Nearly colorless to yellow glasses, IR transmitting   OG Orange glasses, IR transmitting   RG Red and black glasses, IR transmitting   NG Neutral density glasses with uniform attenuation in the VIS   N-WG Colorless glasses with different cutoffs in the UV, VIS and IR transmitting   KG Virtually colorless glasses with high transmission in the VIS and absorption in the IR (heat protection filters)