In addition to our Limited Lifetime Warranty, its most popular features include: Impressively stout appearance sure to enhance your home’s “curb appeal”. Heavy-duty commercial rating for long-term durability and strength. Very tight design resulting in lower air infiltration rates. Strong sash lock system passed 7 different security tests against forced entry. 2 ¾” deep frame and sash feature heavy-gauge walls about 20% thicker than most “builder-grade” windows. Inside glazed with premium solid aluminum glazing bead instead of conventional exterior plastic beads that can crack and warp on aluminum windows. Patented tip-to-tip double "Allerguard" weatherstripping seals the sash in its place for double protection against blowing wind, dirt, dust, and noise. 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.