There are some key differences between studded and studless winter tires. Studless tires work great on slush and packed snow thanks to their wide and deep grooved tread and rubber compound that stays flexible at or near freezing temperatures. Studded tires feature lightweight, small metal spikes (studs) that are staggered and inserted across the tread inside 1/8″ pinholes. These studs protrude slightly from the rubber tread surface, helping break through packed snow and ice-covered roads to give you better traction. However, there are limits to when you can use studded tires. Each state has their own set of rules. See the studded tire regulations guide for specifics.