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About John: John is a Syzjewelry jeweler and business owner with 13 years of jewelry-design experience. This guide shares the figures I work to when a stone is set in prongs.

A prong needs at least 0.45 mm of diameter and should cover 30-40% of the stone's girdle.

The numbers I work to

• Pinpoint prongs: 0.45 mm diameter minimum.
• Girdle coverage: each prong covers 30-40% of the girdle.
• Prong height: 0.3-0.4 mm above the stone's depth.
• Seat: cut 0.05-0.1 mm smaller than the girdle on coloured stones, tighter on diamond.
• Pave: tolerance of 0.02-0.03 mm, about a quarter of a human hair.

The seat

The seat is where the stone sits, and it is the part nobody sees. A coloured stone gets a seat 0.05-0.1 mm smaller than its girdle. Diamond gets a tighter one.

What goes wrong

0.02 mm does not show in a photograph. It shows three months later, on a bathroom floor.

Using this when you shop

• The settings on this page are semi-mounts, meaning the stone is set after.
• If you are having a stone set, ask your setter what seat tolerance they cut to.
• Check the stone size in millimetres on the listing before anything else.

Figures are ranges from my own bench notes. Actual practice follows each workshop's process card, order requirements and the current standard.

Every title says prong, and 22 of the 31 are ring settings. 9 are earrings. Some titles name the prong count, and some also say tulip head or solitaire.

How to choose

• Read the prong count in the title when it names one.
• Match the shape and the millimeters on the product page to your stone.
• The stone is included only when the listing says so.