From the Knit Picks Website:
Choose from any of our soft machine washable yarns to create this fashionable cover-up. Simply determine your gauge and knit a tube that is 8” in diameter and 6” long with ribbing at each end.

Yarn
Knit Picks Swish Worsted
(100% Superwash Merino Wool ; 110 yards/50 grams):
MC - 110 yards
CC - 110 yards

Needles
Size 5: set of dpn
Adjust needle size if necessary to obtain correct gauge.

Notions:
Yarn needle

Design features ribbed edges and stockinette stitch body with stripe accents. Worked entirely in the round on double pointed needles.

Ed. note: Two arm bands could be made by switching MC and CC.

PICC: Peripherally-inserted central catheter