BS 4320 bright metal and black metal washers for use with ISO metric bolts, screws and nuts. The washers are basically divided into 3 categories of size: 'normal', 'large' and 'extra large'. BS 4320 can be rephrased in various ways to convey the same information. One possible alternative could be "British Standard 4320." This revision provides a clearer understanding of the acronym "BS" by expanding it to its full form, while still maintaining the original numerical identifier "4320." By using the expanded form, it becomes more evident that the text refers to a specific British standard, which may be related to a particular industry or field.