Challenge Whipped Butter (available in both salted and unsalted forms) is regular butter with air whipped into it. It has a lighter texture and fewer calories per tablespoon. This product is solid at refrigerator temperatures and requires tempering to enjoy its smooth delicate texture. Because the air content increases the volume of whipped butter, whipped butter cannot be substituted by volume into recipes calling for stick butter. However, whipped butter can be substituted into recipes on an equal weight basis. One tub of Challenge Whipped Butter weighs 8 oz which is the same weight as 2 regular sticks of butter.