The Winter Sottozero Serie II is Pirelli's second generation of Sottozero Performance Winter / Snow tires developed for the drivers of premium, high performance vehicles facing challenging wintertime road conditions. The Winter Sottozero Serie II was developed with the philosophy that winter / snow tires must perform in a variety of unpredictable weather conditions and aren't just for use in the snowbelt states. Winter Sottozero Serie II tires are designed not just as winter / snow tires, but as seasonal tires suitable for the weather and road conditions typically experienced in parts of the U.S. between November and April by providing traction and handling in cold, dry, wet and wintry conditions.Winter Sottozero Serie II tires use a tread compound featuring new polymers and mixing processes that allow them to be ecologically friendlier because they are free of aromatic oils. Pirelli's Temperature Dynamic Compound technology optimizes the compound for wet and icy surfaces to provide improved traction in winter's near-freezing and lower temperatures. The tread blocks feature Pirelli's Interactive Brickwork Siping where the sipes create a brickwork pattern that increases both lateral and longitudinal stability while providing more biting edges to increase snow traction. The tire's internal structure includes twin steel belts reinforced by spirally wrapped polyamide that enhances thermal stability and makes the tires less sensitive to road and air temperature changes.Winter Sottozero Serie II winter / snow tires meet the industry's severe snow service requirements and are branded with the three-peak mountain snowflake (3PMSF) symbol. Install Winter Sottozero Serie II tires in sets of four only.Due to the traction capabilities of the Winter Sottozero Serie II tires, Pirelli recommends using them only in sets of four to provide the best handling characteristics and tire performance. Related Information: What is the three-peak mountain snowflake symbol (3PMSF)?