Oldcastle BuildingEnvelope™'s 1208 Series Thermal Slider Operable Windows are strong, high-performance windows, designed for commercial institutional and residential construction. Hefty main members allow for very large sizes. Cold-rolled steel wheels, set in a sturdy nylon housing, carry the weight of very large sashes. Sash tracks are capped with stainless steel for long-term resilience and to ensure smooth sliding operation. Tank-style sill member assures excellent water drainage, evacuating wind-driven rain under high pressure.