Size guides › Setting styles
Settings
Setting styles, and what actually fits them
Bought new, a setting is usually made to fit the diamond you choose, in any style. A ready-made mounting, or a ring you already have, is different: its head is one fixed size, and a stone outside it rides up on the prongs or sits loose. Here's what each style looks like, and the sizes it's sold ready-made in.
A 1.5 ct oval in six styles, rendered by the tool on the same hand. East–west is shown as it is worn, turned across the finger.
From above, to scale
A 1 ct round in each style, on a millimeter grid, with how wide the whole head is across the finger.
Ready-made head sizes
A ready-made head is sold by the size of stone it holds — a "6.5 mm round" head takes a 6.5 mm round diamond — and the sizes below are read from named listings. Made to order, every style takes any stone Blue Nile sells: 0.20 to 8.00 ct, in every shape. In the tool, the result names the head your stone needs.
| Style | Ready-made heads | Holds about | Source | What it means |
|---|---|---|---|---|
| Solitaire | 4–8 mm | ≈ 0.25–1.90 ct round | RIVA Precision, read 2026-10-19 | Classic single stone. Shows the most of the girdle. |
| Halo | 4–8 mm | ≈ 0.25–1.90 ct round | RIVA Precision, read 2026-10-19 | Accent stones ring the centre. Only the centre seat is modelled. |
| Three stone | 4–8 mm | ≈ 0.25–1.90 ct round | RIVA Precision, read 2026-10-19 | Side stones flank the centre, which tightens the seat lengthwise. |
| Bezel | 5–8 mm | ≈ 0.45–1.90 ct round | Ivy & Rose (listing 1, listing 2), read 2026-10-19 | A metal rim fully surrounds the girdle. Least tolerance for a misfit. |
| Cathedral | 5.85–8.11 mm | ≈ 0.75–2.00 ct round | Estimate — no listing found | Shoulders sweep up to the head, so the stone sits higher. |
| East–west | 5–9 mm across | ≈ 0.25–1.45 ct oval | RIVA Precision, read 2026-10-19 | An elongated stone turned across the finger rather than along it. |
How close a stone has to be. A fixed head takes a stone up to about 0.1 mm over its size, and up to 0.4 mm only by thinning the metal (Ivy & Rose; Brian Gavin gives about the same for ready-made halos). Listings change, so use the figure on the actual product page whenever you have one. The made-to-order range is from Blue Nile, read 2026-10-19.
Why the direction matters
A round head is limited by the stone's width in every direction. A three-stone head is tightened lengthwise by its side stones, and an east–west setting turns a long stone across the finger, so its length is what has to fit. The dimension that matters changes with the style: an oval that sits happily in one may not fit another at exactly the same carat.
Check a stone against a setting
Pick the diamond and the style, and get a plain answer — and the head size to ask for.