Ideally, the windows you choose today should last you for a lifetime, and the Cardinal IG XL Edge spacer system is the best performing and audited system on the market. XL Edge glass units come pre-sealed directly from Cardinal IG. What does this mean to you Other window manufactures simply buy what is known as float glass. This float glass is cut and a sealed unit is created to the standards of the manufactures window factory - resulting seal failure over time. Cardinal IG creates and seals their units directly in their factory - ensuring that only the highest quality and industry leading warranty that is unmatched by any other manufacturer. more... See more text