This is the Facet Keychain pattern by Amy Kate Sutherland of The Graceful Tangle. These keychain wristlets work up super fast and are easy to finish. The pattern is a great way to use up small remnants of cotton yarn. I had a random remnant of this yellow/green/turquoise colorway of Lily Sugar N Cream cotton yarn in my stash. There wasn't quite enough yardage of the colorful yarn to finish two wristlets, so I alternated every two rows with some white cotton for the second wristband.
These would work with a variety of different keychain hardware types. I had these D-ring swivel lobster clasps that I found on Amazon on hand, so that's what I used, but there are many different keychain clasp styles and even ones with prettier finishes available online.
Amy shared this full video tutorial on YouTube: