Made of high quality soda-lime glass, these Microscope Slides are plain, with ground edges and 90° corners. Slides have undergone an automatic cleaning process, which makes them ready for use upon arrival. Slides are supplied 72 per box. Microscope slides are often used together with a cover glass, a smaller and thinner sheet of glass that is placed over the specimen, to hold the specimen in place while protecting the specimen. Microscope Cover Glasses arrive with 100 pieces per box.