High performance and function. Strong and durable long lasting windows Maximum strength & energy efficiency. Strong and rigid long lasting windows. Beautiful and smooth surface finishes. Watertight and airtight window frames. Minimal air infiltration around sashes. Minimal air infiltration at meeting rails. Smooth sash movement and easy tilt. Safe sash operation and inward tilting. Effortless up and down sash movement. Glass cannot be removed from exterior. Minimizes outside noise transmission. Strong secure watertight connections.