Allows "internal chucking" within the range .750" through 1.437". Heads are machinable. Shanks are precision ground to maintain concentricity with +/- .0005". The most effective and accurate means of internal chucking for short runs to mass production. Once seated in spindle and machined to size, these collets can hold concentricity well within .0005". Applicable on any manual or CNC Lathe, Milling Machine or Grinder with a 5C spindle. Machinable to any configuration within their stock and minimum machinable diameters.