| 221 | K7766 | BRITISH STANDARDS INSTITUTION |
| BS1806-221 | K7766 | BRITISH STANDARDS INSTITUTION |
| DEFSTAN02-337-221-HN90 | K0851 | MINISTRY OF DEFENCE DIRECTORATE OF STANDARDIZATION STAN 1 |
| NES 337 | K2516 | MINISTRY OF DEFENCE NAVY SHIPS SUPPORT AGENCY |
| NES 337-1984 | K2516 | MINISTRY OF DEFENCE NAVY SHIPS SUPPORT AGENCY |
| BSM48-221 | K7766 | BRITISH STANDARDS INSTITUTION |
| NES 337-221-HN90 | K2516 | MINISTRY OF DEFENCE NAVY SHIPS SUPPORT AGENCY |
| NES337-221-HN90-(N93H) | U6183 | PRECISION POLYMER ENGINEERING LIMITE |