The frame is manufactured from aluminium and it comes complete with 5 toughened glass slats. You can improve the ventilation in your greenhouse by adding extra louvres. They allow fresh air to enter your greenhouse. This Louvre is designed to replace a piece of glass 610mm x 457mm (2ft x 18"). Please note if you are ordering a new greenhouse at the same time as this louvre, we will automatically adjust the glass in the greenhouse. ..