For the best fit, you should strongly consider custom-sized windows. Custom windows are precision-engineered to 1/8” increments and manufactured to fit your specific window opening. You will get the exact style and options you desire, ensure utmost energy efficiency, and an overall better appearance and installation. Stock-sized windows are adjusted to fit your existing window openings on site and may require extensive carpentry work both inside and outside your home. The appearance and thermal performance can be diminished by this retrofitting process.