Abstract: An improved apparatus for limiting and guiding movement of a window glass panel in a motor vehicle door is provided that minimizes glass contact and drag forces, decouples the material choice between the body portion and guide piece to enable optimization in connection with both the body portion and guide piece, and enables finer tuning of the apparatus merely by incorporating guide pieces of various sizes than by requiring modification or replacement of the entire apparatus. The improved apparatus includes a body portion having a generally U-shaped cross-section, including a base and first and second opposing sides defining a channel. The first side has a pair of longitudinally spaced retaining cavities.