Why call this hat Xylem? The lacy eyelets and other design features reminded me of xylem under a microscope (see here, or check out the Google image search results)! It all seemed to click into place, since the color of this lovely yarn is called Sap -- enjoy! GAUGE 6 sts and 8 rounds per 1 inch (2.5cm) after blocking SIZING / FINISHED MEASUREMENTS Circumference: 21 inches/53 cm (can be blocked larger or smaller) Depth: 8 inches/20 cm. Both measurements are post-blocking.