Adults are usually below 50 cm, very rarely above 60, with females usually larger than males. The smallest European viper. A small, thick snake with a narrow head,. It is usually grayish, pale brown or yellowish with a dark zigzag pattern on the back that is usually bordered in black and can sometimes be broken into freckles. The abdomen may be blackish, whitish or dark gray, even rosy, with or without spots. Melanistic forms (completely black) are possible with this species. They are found at altitudes over 1000m.