A weatherstrip seal comprises a carrier structure without embedded reinforcement that has an attached weather-sealing structure extending therefrom. The carrier structure has two spaced-apart legs connected by a base, the interior walls of the legs forming a channel therebetween. Finger-like members extending from the walls are adapted to frictionally engage and hold a mounting flange inserted into the channel. The legs decrease in thickness as they proceed outwardly from the base and their walls converge inwardly toward each other, minimizing the material required for fabrication of the carrier and enhancing its ability to withstand forces acting to dislodge the mounting flange from the channel, especially at corners thereof.