Our single hung window, also known as The Ultimate Window, blends energy performance with hurricane protection, giving you the best of both worlds. Blends energy efficiency with impact options Two panes of double-strength eVantage™ 366 Low-E Glass Lower sash operates and tilts in, upper sash is fixed Upper fixed sash can include arch top as an option Premium uPVC vinyl for long-lasting thermal performance Self-locking mechanism for extra security