Keller produces Riesling from Rheinhessen, Germany's largest wine region. The winery's focus centers on noble late-harvest expressions: Trockenbeerenauslese and Auslese wines from vineyard sites including Westhofener Morstein and Dalsheimer Hubacker. These concentrated, sweet Rieslings represent the apex of botrytis-affected fruit, where noble rot concentrates sugars and complexity. The Westhofener Morstein Riesling Trockenbeerenauslese and Dalsheimer Hubacker Riesling Trockenbeerenauslese both achieve 97-point averages from prestige critics including Wine Spectator and Wine Enthusiast. The Riesling Auslese from Westhofen Morstein reaches 96 points. Such scores reflect the precision required to craft these wines—timing harvest to optimal ripeness, managing fermentation of high-sugar must, and balancing residual sweetness with acidity. Rheinhessen's warm continental climate and slate-rich soils provide ideal conditions for Riesling's aromatic intensity and the fungal pressure that enables noble rot development.