Reinforced plastic composite articles which have a non-constant cross-sectional shape over their length, such that a first portion of the article has a different cross-sectional shape than a second portion of the article, and which portions may be integral with each other. In one embodiment, the article may have a non-constant cross-sectional shape with a constant cross-sectional volume over its length. In another embodiment, the article may have a non-constant cross-sectional shape and non-constant cross-sectional volume over its length. An apparatus and a method which utilizes a die having a die channel of non-constant cross-sectional shape is employed. In the apparatus, a pair of first and second die-forming members are used, and form in one or both of the die-forming members a die channel having a first portion of a cross-sectional shape which is different than a cross-sectional of a second die channel portion over the length of the die channel. One of the die-forming members may move relative to the other or both may move together at a constant speed in order to effectively pultrude a reinforced plastic composite article.