Dunlop tempered glass slides for a bright tone with a beautifully detailed high end. Processed from high quality boron silicate, heat treated and annealed to produce a flawless tube, this is our most popular slide available. Dunlop 211 SI Glass Slide Heavy Heavy Wall Thickness - Small Choose Dunlop tempered glass slides for a bright tone with a beautifully detailed high end. Processed from high quality boron silicate, heat treated and annealed to produce a flawless tube, this is our most popular slide available. Heavy Wall Thickness - Small (17 x 25 x 69mm)