Thermalux foam heat retention covers are manufactured from a closed-cell PE foam. 12mm Thermalux is suited for all heat retention purposes on pools up to 30°C and benefits from a laminated underside and strong woven polyethylene top coat, making it extremely hard wearing. The density of the material helps to keep light penetration to a minimum and therefore reduces algae growth. ** Please note all Thermalux covers are made to order, current lead time is approximately 4 weeks **