Twin Wall Weathering Gas Cap (12G) - 100mm Dia Zoom Twin Wall Weathering Gas Cap (12G) - 100mm Dia SKU: 03011012GDW. A GAS terminal that protects the insulation of the chimney and provides an unrestricted discharge to the atmosphere - requires a locking band Availability: In stock £77.99 Qty: Add to Cart Email to a Friend Additional Information Additional Information Additional Information SKU 03011012GDW Diameter 100mm (4") Components Terminals CMS tab x Add to Cart Price: Actual Price: Our price is lower than the manufacturer's "minimum advertised price." As a result, we cannot show you the price in catalog or the product page. You have no obligation to purchase the product once you know the price. You can simply remove the item from your cart. Our price is lower than the manufacturer's "minimum advertised price." As a result, we cannot show you the price in catalog or the product page. You have no obligation to purchase the product once you know the price. You can simply remove the item from your cart.