These are highly flexible resilient elements that can reach a travel of dozens of millimetres. They can be made entirely of rubber or rubber-bonded metal. 
Their geometric shape can be cylindrical, coaxial or double wedge to be mounted on coupled elements. 
They used as primary and secondary suspension elements, mainly on trams and underground trains. 
They have a high internal damping, they can absorbe high peaks of load and allow for a progressive telescoping.