A slat for use in a roller shutter has an elongated body. The elongated body has an upper engaging arrangement in an upper portion thereof, and, a lower engaging arrangement in a lower portion thereof. The body is provided with at least one chamber having at least one bar. The at least one bar of a given slat has a vertical overlap with the at least one bar of the slat that is engaged with the given slat and upwardly therefrom. When the slat has a first bar within an upper chamber and a second bar within a lower chamber, the first bar overlaps with the second bar in a lengthwise direction along an internal overlap.