---
category: Foundations
---

`hairline` is the ink at 8% and `strong` at 12% — 1.17:1 and 1.28:1 on `--surface` —
drawn at `--rule-w` (1.25px), which is the only border width the reference uses.

**A hairline is never the only separator.** Both values sit far below every floor there
is, so the region a rule bounds must also change field, gain a label, or gain space.
That is a ban in the pack rather than a preference.

```tsx
<Rule />
<Rule tone="strong" />
```