Needle roller bearings (848240) use rollers whose length is at least three times their diameter, giving them a needle-like profile suited to high-load, compact applications. Cylindrical roller bearings (848250) have rollers with a smaller length-to-diameter ratio. The physical dimensions of the rolling elements, not the application, determine the subheading.

Yes — 848291 specifically covers balls, needles, and rollers for ball or roller bearings when imported separately. These rolling elements are not classified as raw material or as parts of machines; they belong under 8482 because the heading explicitly includes parts of bearings.