It has a clamping range of from 3/32" (2 mm) up to 1-1/2" (38 mm) diameter with the jaws in the normal position. With the jaws in the reversed position, work up to 2-3/4" (70 mm) can be gripped. The hole through the chuck is .687" (17 mm). A hex key (provided) is used to tighten each jaw individually. A groove is machined around the base of the chuck so that angle clamps can be used to mount it to the table of a mill as a holding fixture. The chuck has a 3/4-16 thread to fit Sherline's spindle and other machines using that thread.