Basic Done Beautifully^®. Pella^® ProLine^® offers a beautiful collection of windows and patio doors with our most popular choices—including a wide range of standard sizes, shapes, styles and exterior cladding colors. And great features like prefinished white interiors and a variety of grille types and patterns. Best of all, they're low-maintenance and remarkably energy-efficient. ProLine products with Low-E insulating glass are ENERGY STAR^® qualified. All this at a competitive price.