GN 743.6 Aluminum Fluid Sight Glasses, with ESG Safety Glass, ATEX Explosion Protective. GN 743.7 Brass Fluid Sight Glasses, with Float Glass, with Conical BSPT or NPT Thread. GN 743.8 Brass Fluid Sight Glasses, with ESG Safety Glass, with Conical BSPT or NPT Thread. GN 744 Aluminum / Crystal Clear Plastic Fluid Sight Glasses. Welcome to The Glassblowing Shop, a retail glass gift shop with five locations, operated by a family of glass artists with over 60 years of experience. The majority of our glass gifts are made using the methods of Flamework glassblowing, Furnaceworking and Stained Glass work, and all items are original hand blown creations by our artists .