| Members | National Metrology Institutes | M |
| Associates | with observer in the GA | A-GA |
| Corresponding Applicants | A-CA | |
| Designated Institutes | A-DI | |
| Liaison Organisations | Regional Metrology Organisations | LO-RMO |
| Corresponding NMIs | LO-NMI | |
| Corresponding Organisations | LO-CO |