Ceramic Refractory insulated Strip heaters are sheathed in rust-resistance steel or in stainless steel sheath as it provide physical strength and good thermal conductivity. Specially selected and designed ceramic insulator houses the resistance wire insulating it from the outer sheath. Finned strip heaters are used for both forced (mounted in ducts) and natural convection air heating (mounted at the bottom of cabinet type oven). The fins provide maximum surface contact for good heat dissipation into the finned cross section thus resulting in rapid heat transfer to the air.