The Polypropylene stacking chair or “Polyprop” is a chair manufactured in an injection molding process using polypropylene. It was designed by Robin Day in 1963 for S. Hille & Co. Polypropylene had been invented in 1954 by Italian scientist Giulio Natta but it had not been used in the furniture industry before. Robin Day and Hille looked to develop seating using this new durable, cost efficient material working in conjunction with the British petrochemical company Shell. This is one of the very few chairs that after over 40 years is still in production and has been made in 40 countries around the world, for schools, hospitals, airports, canteens, restaurants, arenas, hotels, as well as homes. It is the best-selling chair in the world. It is now so iconic that it was selected as one of 8 designs in a 2009 series of British stamps of “British Design Classics”. Inspired by the Eames ”Plastic Shell” Robin Day developed this low cost, stackable, single-form seat. The seat is made from polypropylene which is inexpensive, durable, lightweight, easy to clean thermoplastic. A single injection mold can produce 4000 seat shells per week. From 1963 to the present day over 14 million Polyside chairs have been sold. The chair first appeared on the market in a choice of charcoal or flame red colors at a little under £3 in price. The side chair won a Council of Industrial Design (now the Design Council) award in 1965. The brief from Hille was for a low cost mass-produced stacking chair, affordable by all and to meet virtually every seating requirement. Over time it became available in a wide variety of colors and with different forms of base and upholstery. These variations have included “Series E” for children, made in 5 sizes with lifting holes, and “Polo” with rows of graduated circular holes making it suitable for outdoor use.