Trending Baby Hat Knitting Pattern 4Mm Needles - 6 (4 mm) knitting needles or size needed to obtain gauge. Change to 4mm (us size 6) needles and starting with a knit row work in stocking stitch for 16(20). Baby Hat Knitting Pattern 4Mm Needles : Bind off by k2tog every five stitches until you have one stitch left on your needles.