Comprised of 45 couplings offered in inch and metric sizes, S51FCZ Series joins shafts from .0900-.2498 in. (2.5-12 mm) dia. Inch to metric or metric to inch couplings are also available. Made of 303 stainless steel, zero backlash couplings are readily adjustable on shaft and feature compact, self-contained Fairloc® hub fastening system, which eliminates marred shafts while adding positive metal-to-metal fastening strength along both hub sections.