# The Road Vehicles (Display of Registration Marks) Regulations 2001, Paragraph 6


The markings required under paragraph 5 must be—
(a) permanently marked;
(b) non-retroreflecting;
(c) of a single shade of non-retroreflecting colour; and
(d) no more than 10 millimetres in height and no less than 3 millimetres in height.

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Source: https://www.legislation.gov.uk/uksi/2001/561/schedule/2/paragraph/6 (the official version)
Page: https://openlegislation.uk/road-vehicles-display-of-registration-marks-regulations-2001/schedule-2/paragraph-6
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.