As their name suggests, rye beers are brewed with at least 20% rye malt and varying degrees of bitterness, although moderate to high hopping levels tend to draw out the unique tart rye flavors in an American rye ale. Their appearance can range from straw and amber to darker amber and brown colors when roasted malts are used. While rye is the most assertive malt that can be used in brewing, rye ales can still be comparable to an American wheat beer. A specific German substyle of rye beers is the roggenbier, which originated in Regensburg, Bavaria. The roggenbier is normally brewed with less hops, is unfiltered, and utilizes yeasts that produce phenolic (clove-like) and fruity ester (bananas and citrus) character (much like a hefeweizen or dunkelweizen).