Waterproof classic boot.If you are unsure which shoe size to purchase, please follow the following steps:1)Draw a straight line, longer than your foot, on a piece of paper.2)Place the paper on a flat surface. Stand on the line with your heel and longest toe centered on the line. If measuring a child's foot, it may be easier to hold the paper up to their foot.3)Place a mark on the line at the tip of the longest toe and at the back of the heel.4)Repeat steps 1-3 for the other foot.Measure the distance between the marks. Taking the larger of the two measurements.