Callisto Hat is a squishy, entirely reversible hat worked in a twisted rib and with just a touch of colourwork.
The double brim can be turned up for more of a beanie or worn down to show off the colourwork. A sibling of Callisto Gloves/Mitts, Callisto Hat makes a brimming trio together with Simple ZigghurHat & Kaul Toque in the Hatalogue eBook.
Useful photo tutorials that are linked in the pattern:
Winding Provisional Cast On (scroll to bottom for special instruction for looping around to create a closed top)
No-sew knitting lining for hems & brims
Make 1 Left/Right purl (and knitted)
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Shown in Wollmeise Merino DK. A suggested substitute is below.