Spring loaded aluminum back draft damper prevents drafts from entering back into the room. Metal 8 in round diameter housing, vents directly to outside, includes spring-loaded aluminum back draft damper for maximum air flow. Direct to outdoor exhaust designeliminates the need for ducting. White polymeric grill. Dimensions: 11-1/2 in x 11-1/2 in One piece polymeric wheel. UL Listed. HVI2100 Certified.