Watch Glass (Beaker Cover), Pack of 12 Watch glasses are highly functional laboratory glassware that have a variety of uses in the classroom or lab. The concave dishes are designed in a variety of sizes, our watch glasses work well as lids for flasks and beakers, or holding small samples for observation under a low-power microscope. These watch glasses are ideal for evaporating liquids off of samples, such as growing seed crystals. They can be used for making lenses of ice or other liquids. Their 2.0 mm thick construction resists shattering. And as they have ground edges, as well as a polished surface, you can be sure that they are a safe product to handle in the classroom or the lab.