What is kraft paper made of?

A long time ago, "kraft paper" was really made from calf skin. Of course, this "kraft paper", now only in the time of making drum skins, will use it;

Kraft paper is made of coniferous wood sulfate pulp texture tough, strong, yellowish-brown high-strength wrapping paper, from the appearance of light can be divided into a single-side light, double-sided light, striped, stripe-free varieties, the quality of Requirements are slightly different. Kraft paper is mainly used for the production of small paper bags, bags and industrial products, textiles, daily necessities of the inner packaging.