Weight rings (also called flask weights or flask weight rings) are donut/ring-shaped rings, made of lead and covered with polyvinyl chloride or silicon. It is to be fitted overa flask or measuring cylinder filled with liquid in order to prevent its spillage while in a water bath. By preventing spillage it both maintains the accurate volume of the liquid and protects bench-tops and lab-wares. It also provides stability to the flask and prevents it from floating. The covering makes the ring chemically inert and does not cause any scratch to the equipment either.

It is available in bright colors for easy recognition. It comes in various diameters to suit Flask/Measuring Cylinder of different volumes. It is steam resistant and autoclavable and has a very long lifespan.