A motion guide device includes a ball nut attached onto a shaft and having helical grooves for receiving ball bearing elements, and a ball coupler including a flexible coupling member having a number of openings formed between spacers for receiving ball bearing elements, the ball bearing element is contacted with the ball nut at a contact point which is spaced from the inner peripheral surface of the ball nut for a spacing distance, and the ball bearing element is contacted with the screw shaft at a contact point which is spaced from the outer peripheral surface of the screw shaft for a spacing distance that is preferably smaller than the spacing distance between the contact point of the ball bearing element and the ball nut.