Microscope cover glasses are made of pure white borosilicate glass with excellent chemical resistance and flatness, and are free of bubbles and scratches.VWR supplies cover glasses and coverslips for the protection of lab samples on microscope slides. Cover glasses constructed of borosilicate glass are of uniform size and thickness. Corrosive and chemical resistant models feature no bubbles or scratches. Select coated options for non-stick performance in humid conditions. Cover glasses are offered in round, square, and rectangular options in standard numbered thicknesses. Some coverslips are prepackaged by weight in boxes;