Twin Wall test unit (050) - 200mm Dia Zoom Twin Wall test unit (050) - 200mm Dia SKU: 20050DW. Section of flue with test point Availability: In stock £131.99 Qty: Add to Cart Email to a Friend Additional Information Additional Information Additional Information SKU 20050DW Diameter 200mm (8") Components Accessories 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.