Pella 150 Series sliding window in white vinyl, measuring 47.5" W x 47.5" H in an XO configuration (one sliding vent panel, one fixed panel). Features Low-E 180/Clear annealed glass with argon gas fill optimized for high altitude use. NFRC certified with excellent energy performance: U-Factor 0.30, Solar Heat Gain Coefficient 0.53, and Visible Transmittance 0.64. Includes matching screen. Never installed, in original box, no damage reported. Ideal for Colorado homes requiring altitude-optimized insulated windows.