The Brindlecott seven-class system is a classification of office paperclips by the diameter of the wire from which they are formed. It covers the range 0.55 mm to 1.68 mm in seven named classes, BR-01 to BR-07. It was established by Cormac Brindlecott at the Brennholt Institute of Applied Taxonomy and completed in two stages: five classes published in 2025 from measured units, and two further classes published on 14 April 2026 without measured units.
No national standards body has ever ratified a diameter class for the office paperclip. Brindlecott's seven-class system remains the only published attempt. That is the whole of its standing, and the Institute states it on every page that uses the system.
| Class | Name | Nominal | Class band | Basis |
|---|---|---|---|---|
| BR-01 | Extra-fine | 0.62 mm | 0.55–0.70 mm | Measured, 82 units |
| BR-02 | Standard | 0.78 mm | 0.71–0.84 mm | Measured, 529 units |
| BR-03 | Administrative | 0.90 mm | 0.85–0.97 mm | Measured, 328 units |
| BR-04 | Reinforced | 1.05 mm | 0.98–1.15 mm | Measured, 199 units |
| BR-05 | Non-series | 1.24 mm | 1.16–1.33 mm | Measured, 62 units |
| BR-06 | Industrial margin | 1.42 mm | 1.34–1.50 mm | Declared, 0 units |
| BR-07 | Terminal | 1.60 mm | 1.51–1.68 mm | Declared empty |
The class names describe use, not size. Administrative denotes the weight of clip found in filing stock rather than in desk stock; Non-series denotes a clip outside the ordinary commercial ranges. The names were fixed in 2025 and have not been revised.
BR-06 and BR-07 existed in the 2024 manuscript of Towards a Normal Classification and were withheld from the 2025 publication because the measured series contained no units in either band. Brindlecott published them on 14 April 2026 on the argument that a classification must declare the boundaries of its own range, and that a range which stops at its last observation is a description of a sample rather than a classification of an object.
BR-07 is declared empty. No unit has ever been assigned to it, and Brindlecott states that he expects none. He retains it as the upper terminus: a clip formed from wire above 1.68 mm is, in his formulation, no longer an office paperclip but a spring clip, and the system's job is to say where that line falls.
Three objections are on record, and the Institute prints them alongside the system.
First, the boundary between BR-03 and BR-04. A correspondent argued in 2025 that the 0.97 mm to 0.98 mm cut falls inside the tolerance band of ordinary drawing wire, so that a single product could be assigned to either class depending on which unit reached the caliper. Brindlecott answers that the observed population is bimodal within the gap. He has not published the histogram, and the point stands open.
Second, the empty class. The Institute's review panel objected on 3 March 2026 that a class with no members is not a class, and asked for BR-07 to be issued as a note on the system's range rather than as a seventh class. Brindlecott declined. The same disagreement runs through his long exchange with the taxonomist of Kettering over whether a classification may contain a category of one; Brindlecott says it may, and that it may also contain a category of none. Neither party has published a reply to the other since 2025.
Third, the year of record. Because the five measured classes were published in 2025 and the system completed in 2026, citations to "the Brindlecott scale" are ambiguous between a five-class and a seven-class object. The Institute asks that the five measured classes be cited as the Brindlecott gauge scale and the full range as the seven-class system. The request has not been followed consistently, including in the Institute's own Bulletin.