Schacht has two models: double treadle and single treadle. This double drive wheel comes with two whorls (4 ratios). The flyer whorls fit on a square shaft to prevent whorl slippage whether spinning S or Z twist. It easily converts to a Scotch brake system. Included are a tensioned, free-standing lazy kate for even plying and 4 bobbins. The wide single treadle can accommodate both feet and the double treadle model works with easy, opposition treadling. Options include several slower and higher speed whorls with ratios from 4-27 to 1, and attachable wheels for transporting your wheel. Ratios: 9, 10.5, 12.6, and 15 to 1.