In addition to our Limited Lifetime Warranty, its most popular features include: Full screen is standard, allowing full ventilation with both sashes open. Consider optional Full Solar Screen for added protection against solar heat gain. Heavy-duty commercial rating for long-term durability and strength Very tight double-hung design exceeds tough ANSI/AAMA 101-85 standards. Strong sash lock system for added security. 3 ¼” deep frame and sash feature heavy-gauge walls about 20% thicker than most “builder grade” residential windows. Glazed with full perimeter marine glazing boot that protects and further insulates the glass seated inside the sash frame. Patented tip-to-tip weather stripping seals the sash in place for double protection against blowing wind, dirt, dust, and noise. Commercial adjustable balancers with exclusive top sash clamp ensure long-lasting operating function of both sashes. Environmentally friendly, VOC free durable powder coated finish for long lasting color retention.   Glazing Options We strongly recommend our Energy Star™ compliant insulated glass package that combines Guardian's ClimaGuard RLE Low E Glass with patented Dual-Seal™ butyl spacer system with Argon Gas for enhanced energy efficiency. Patented DuraSeal™ butyl spacer is standard. Cardinal's XL Edge™ Dual Seal Stainless Steel Spacer Systerm with Argon Gas is optional. Obscure and tinted glass. Choose from standard and Contour Grids, or no grids. Colonial, Prairie Lite, and custom grid patterns.