This is a ribbed, reversible cable pattern - 24 stitch cast-on, 8 stitches per cable. The knit 1, purl 1 rib is what enables it to be reversible. The ends are grafted together, making it a large circular shape that can be wound around the neck several times. There is one size - using around 200 yards, it is about 59-60 inches long.
You can use any weight yarn, just use appropriate needles to obtain gauge.