This larger chuck takes up no more center-to-center space than the 2.5" chuck, but it will hold larger work.
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.