Retro Fit or Replacement window refers to the type of installation used and frame style. This type of window is designed to be inserted into an existing window frame. In most cases this type of install can be done in one day with no exterior or interior wall damage. Retro fit windows have an exterior flange that allow them to cover your old window frame. With a quality installation performed by our factory trained and certified installers we offer a lifetime warranty on the installation. We have several top manufactures to choose from so we can give you more than one option and price to fit your needs.