An attachment 10 mountable to an electric toothbrush handle 62 having a drive shaft 60 comprises a neck member 16 having an elongated body 40 with a principal axis 42 and a cavity 44; a slide member 12 with an engagement surface 22; a guide sleeve member 14 having a cavity 84, a first outer surface 88 with an engagement opening 90, and a transition surface 92; and a collar member 18. The guide sleeve member, with slide member moveably inserted within the engagement opening, is moveably inserted within the neck member cavity. Insertion of the drive shaft into cavities of the collar member and guide sleeve member from (a) a first radial position along an axis offset and parallel to the principal axis to (b) a second radial position in-line with the principal axis, via the transition surface, results in the drive shaft being held in frictional contact with the engagement surface of the slide member to enable reliable transfer of force/motion from the drive shaft to the neck member.