# DIN 6921 — DIN / ISO / BS fastener equivalents and the sizes where they are not interchangeable

For DIN 6921, iso standard is DIN EN 1665; part is Hex Head Bolts with Flange; interchangeability verdict is Check spec, verified against its source on 2026-08-05.

- **DIN standard:** DIN 6921 _(verified: appears in the quote below)_
- **ISO standard:** DIN EN 1665 _(verified: appears in the quote below)_
- **Part:** Hex Head Bolts with Flange _(verified: appears in the quote below)_
- **Interchangeability verdict:** Check spec _(verified: appears in the quote below)_

## What the source says

> Hex Head Bolts with Flange | DIN 6921 | DIN EN 1665 | Check spec | Flange OD/serrations/tolerance windows.

## Sources disagree

More than one authority states this, and they do not state the same
thing. Both are reproduced with the source each came from.

### ISO standard

monsterbolts.com says iso standard is **DIN EN 1665**, as of 2026-08-05.

> Hex Head Bolts with Flange | DIN 6921 | DIN EN 1665 | Check spec | Flange OD/serrations/tolerance windows.

Source: https://monsterbolts.com/pages/common-din-numbers-for-metric-fasteners

trfastenings.com says iso standard is **ISO 1665**, as of 2026-08-05.

> DIN 6921 | ISO 1665 | | Hexagon Flange Bolts |

Source: https://www.trfastenings.com/knowledge-base/engineering-data/fastener-standards


### Part

monsterbolts.com says part is **Hex Head Bolts with Flange**, as of 2026-08-05.

> Hex Head Bolts with Flange | DIN 6921 | DIN EN 1665 | Check spec | Flange OD/serrations/tolerance windows.

Source: https://monsterbolts.com/pages/common-din-numbers-for-metric-fasteners

trfastenings.com says part is **Hexagon Flange Bolts**, as of 2026-08-05.

> DIN 6921 | ISO 1665 | | Hexagon Flange Bolts |

Source: https://www.trfastenings.com/knowledge-base/engineering-data/fastener-standards


## Source

- https://monsterbolts.com/pages/common-din-numbers-for-metric-fasteners
- https://www.trfastenings.com/knowledge-base/engineering-data/fastener-standards

Last verified: 2026-08-05. Review by: 2029-08-04.
Part of [DIN / ISO / BS fastener equivalents and the sizes where they are not interchangeable](https://referencesource.org/fastener-standard-interchangeability-exceptions/).