5" W x 33" H• IMPORTANT: always keep mesh panels closed and glass doors OPEN when fire is burning in the fireplace• For masonry fireplace only - not for prefabricated These fireplace glass doors are designed as a surface mount as an overlap design - For masonry fireplaces only - not for prefabricated.. Features:• Glass doors reduce cool air and heat loss up the chimney by as much as 90% when fire is not in use• Three-sided bay design one-piece steel frame construction with high-heat powder coated finish for looks and durability• Bifold-style track-free doors close with easy-catch magnets to provide energy efficiency• Safety Tempered 3/16" Smoked Glass• Rigid mesh screen panels with catch magnets help keep embers and sparks contained• Includes: Easy grip handles, premium fiberglass insulation and hardware assembly kit Before you buy choose small, medium or large - Measure front opening width and height to choose the correct size - Check both measurements and be sure they are accurate to the nearest 1/8”Size Medium• Fits 30" - 37" W, 25-1/2" - 32-1/2" H openings• Overall glass door frame dimensions: 37.