Opti Therma Foam Slats are made of rolled aluminum strips stuffed with a layer of insulating foam to provide more thermal and sound insulation. The foam layer is normal for small sizes or high density for large and medium sizes. They are available in multiple colors but are limited and cannot be repainted. There are German-made ones from HEROAL or Kuwaiti-made ones from ALUSOL; they are low-noise compared to drawn feathers.