H.18D is for use with only 2.35mm (3/32″) shank burs. A press lever action is all that is required to change accessories. It features a very slim grip and pre-lubricated ball bearings that do not require any lubrication.18D has the same specs as the H.18, except includes a duplex spring for added flexibility.  10-3/8″ long, 19/32″ dia., wt: 5.3 oz., Duplex springs are subject to breakage and are NOT covered by warranty. They are made of special steel, double wound tubular construction with a protective flexible spring cover. Replacement springs (HP76) are available and can be installed by the user.  Please call us for additional Foredom items or parts not listed on this website.