MuscleChuck Camless Quick Change 1/2-Inch Chuck for Porter Cable 630, 690, 691, 693, 890, 7518, 7519, 7536, 7537, 7538, 7539 ONLY Type 1:Fits Porter Cable; 630, 690, 691, 693, 890, 7518, 7519, 7536, 7537, 7538, 7539. 1/2-inch shank can use bushings for 1/4-inch, 8mm and 3/8-inch shanks. Length: 1.3 in (Approx) Run Out: &lt;.002 in High Quality Alloy Steel. All materials and processes certified to aircraft standards.