watch glass is a circular concave piece of glass used in chemistry as a surface to evaporate a liquid, to hold solids while being weighed, for heating a small amount of substance and as a cover for a beaker. The latter use is generally applied to prevent dust or other particles entering the beaker, the watch glass does not completely seal the beaker, so gas exchanges still occur. 

* Sturdy Glass: Concave beaker covers (also known as watch glass).jpg made with quality glass. Each cover features ground edges & polished surfaces. 

* High Transparency: Features excellent transparency, clear observation of liquid changes and experimental results while ensuring durability. 

* Multifunction: Great for evaporation, holding samples, covering beakers and flasks. * Safe: The glass is also designed with durability, featuring smooth edges and rounded curvature for safe handling.