Answer:
A circular iron rod with a clamp for use on a ring stand.
Step-by-step explanation:
An iron ring is a circular iron rod that has a clamp that can be used to mount it on a ring stand. The iron ring serves to hold glassware, such as a flask, so that the glassware will not tip over, and is usually employed when the glassware may need to be heated, such as a Bunsen burner that can be placed underneath.