Since it is part of the Duplet superfamily, you can combine Duplet Open with its relatives: Duplet and Duplet Rounded. Each contains seven weights ranging from Thin through ExtraBold, all with companion italics. The fonts include more than 450 glyphs, covering all the European languages written with the Latin script.

Since the Duplet Open fonts are geometric, the round characters and round-parts of letters appear either as circles or slanted circular forms (like you see in the italics). Duplet Open’s letterforms are very low-contrast with strokes that seem even in thickness. On letters like ‘e’ and ‘s’, the strokes also end in diagonal shears rather than horizontals. That makes the letters’ counters more open. They render a little less dark and may even be slightly more legible at small sizes or on screen than ITF’s Duplet family.

The default form of the ‘a’ in each font is single-storey. The large round bowl drives Duplet Open’s inherent geometry home! But there is a double-storey ‘a’ as an OpenType alternate ‘a’. The default ‘g’ is also single-story, and its bottom stroke is flattened, giving it a streamlined, less-complicated look. Duplet Open’s fonts feature three more ‘g’ versions as alternate characters.

There are alternates for ‘k’, ‘u’, ‘G’, ‘K’, and ‘M’, as well as the ampersand (&). The character sets include case-sensitive forms, too — punctuation marks that are vertically repositioned and look better in all-caps texts. When it comes to numerals, both proportional and tabular lining figures are there, as well as fractions, superior numerals, and inferiors. Diana Ovezea and Rafał Buchner designed this typeface with great attention to detail.