# The Traffic Signs Regulations and General Directions 2016, Paragraph 4

Extent: E+W+S

Each lens must be of such a shape and size that the perimeter of its area projected horizontally onto a vertical plane is capable of lying wholly inside a square having sides of 200 mm in length and wholly outside a square having sides of 100 mm in length.

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Source: https://www.legislation.gov.uk/uksi/2016/362/schedule/13/part/10/paragraph/4 (the official version)
Page: https://openlegislation.uk/traffic-signs-regulations-and-general-directions-2016/schedule-13/part-10/paragraph-4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.