An iron ring or ring clamp is a lab item comprised of a metal ring-like loop, used to hold various lab equipment, that usually cannot be placed on flat surfaces, such as funnels, Imhoff cones, sometimes even round-bottom flasks.
The iron ring consists of a metallic rod connected to a screw clamp, which loops in a circle. Some models have the metal rod welded to itself, while other iron rings are not. A similar type has a space between the tip of the rod and the rest of it, giving it a question mark-like shape. This type is called open ring and is commonly used for holding separatory funnels, when its desired to prevent any drops of reagent from reaching the iron ring and affecting it. Not all iron rings have a screw clamp.
As their name suggests, iron rings almost always made of cast iron or carbon steel, which is covered in chemically resistant paint or are nickel-plated. Iron rings are rarely made of stainless steel or other alloys.
Iron rings can be bought from lab suppliers or online.
DIY iron ring
A very simple iron ring can be made by carefully bending an iron rod, then placing it in a bosshead.