Die and mold production bushings reduce friction and wear between parts. They come in plain and ball bearing forms. Plain bearing bushings are sleeve-shaped liners that absorb the friction of rotating shafts. They are less durable than ball bearings because they lack rolling elements to reduce wear but they self-lubricate and are made of tough materials. Most plain bearing bushings are solid sleeve bushings, but split and flanged forms exist to make installation easier. Ball bearing bushings carry loads and reduce friction on gears to let them spin more easily, which increases operation speed. Die and mold ball bearing retainers house and equally separate the bearing's rolling elements so the bearing can carry loads. Without the retainer, the bearing would fail during operation.