We provide two types of Polypropylene which is less expensive and UPVC (Un-Plasticized Polyvinyl Chloride) which is more expensive. UPVC is far superior to Polypropylene in every aspect except for the price. It's your choice. Polypropylene is more economical and UPVC is strong, durable and weather-resistant, making it ideal for outdoor use. See the chart below for some comparisons.