The Plantronics foam cushion (pictured at lower right) is a great solution for headsets that have earloops like the OfficeRunner, CS50, CS55 (DISCONTINUED), Calisto (DISCONTINUED), GN9125, and GN9350. Catalog # 9255.
Tip: The more, the merrier! Using more than one cushion typically adds even more comfort
For more stability, another great option is the OfficeRunner Foam Earloop Cushion!
(pictured at upper right) Catalog # 2183