It's a ribbed knit stitch that uses slipped stitches and is probably reversible. You could work over a multiple of 4sts + 1. I think
row 1 repeat (Sl1, k, p, k) ending sl1
row 2 rrepeat (p, k, sl1, k) ending p1
will give you something close. The neck warmer in the picture is worked with 2 strands of yarn held together.