The Westbrass air gap shields the dishwasher's dirty water from backflowing into your dishwasher and onto your clean dishes. The air gap also shields the dirty water from overflowing into your main water lines, as required by code in many states. Cast brass construction skirted air gap cap only. The skirted cap covers the entire air gap body and is installed flush with to sink. Available in a variety of stylish finishes, this item is sure to complement your existing fixtures. Westbrass Fine Decorative Plumbing since 1935.