CapitolBrand M3504-E Borosilicate Glass Economy Grade Plain Microscope Slides, 3" Length x 1" Width x 1mm Thick (Box of 72)
Ready to use out of the box, with no preparation or cleaning required.  Ground smooth edges provide a smooth finish to reduce the likelihood of injury.  Cost effective economy grade glass, suitable for most general applications.  Made of clear glass and not frosted to provide a large sample area.