Horizontal mixers often use three roller bars to develop yeast-raised doughs; however, horizontal mixers also can feature single-sigma or double-sigma agitators to mix doughs for a variety of products.

Sigma mixers are commonly used for cookie and cracker doughs, as well as biscuits, corn tortillas, granola and snack bars, and sweet doughs. Double-sigma mixers often produce firmer cookie doughs that likely will be portioned using a wire-cutter, while rotary-moulded cookie dough is generally mixed using single-sigma mixers.

Topos Mondial Corp., Pottstown, PA, and Shaffer Manufacturing, a Bundy Baking Solutions company, Urbana, OH, both offer open-frame horizontal sigma mixers. Sigma mixers increasingly feature variable-frequency drives. Ed Fay, president of Joliet, IL-based CMC America, described sigma mixers as the most versatile horizontal mixers. Most horizontal mixer manufacturers offer both roller bar and sigma styles.