DuoDERM Extra Thin CGF (Control Gel Formula) Hydrocolloid Dressing, Sterile. DuoDERM Extra Thin dressing is a hydrocolloid dressing indicated for the management of lightly exuding wounds. It combines a unique ConvaTec hydrocolloid formulation that distinguishes it from other hydrocolloid dressings and a vapor-permeable outer film to provide an occlusive moist environment.