The traditional clothing system developed and used by the Yup'ik and other Northern Indigenous peoples is the most effective cold weather clothing developed to date. Yup'ik clothing tended to fit relatively loosely. Skin sewing is artistic arena in which Yup'ik women and a few younger men excel. Yup'ik women made clothes and footwear from animal skins (especially hide and fur of marine and land mammals for fur clothing, sometimes birds, also fish), sewn together using needles made from animal bones, walrus ivory, and bird bones such as front part of a crane's foot and threads made from other animal products, such as sinew. The semilunar woman's knife ulu is used to process and cut skins for clothing and footwear. Women made most clothing of caribou (wild caribou "Rangifer tarandus granti" and domestic reindeer "Rangifer tarandus tarandus") and sealskin. The English words kuspuk (parka cover or overshirt) and mukluk (skin boot) which is derived from the Yup'ik word "qaspeq" and "maklak". Before the arrival of the Russian fur traders (promyshlennikis), caribou and beaver skins were used for traditional clothing but Northern Indigenous peoples were compelled by to sell most of their furs to the Russians and substitute (inferior) manufactured materials. Everyday functional items like skin mittens, mukluks, and jackets are commonly made today, but the elegant fancy parkas ("atkupiaq") of traditional times are now rare. Today, many Yup'ik have adopted western-style clothing.