Heres a couple of pics of my studded tires. Both pairs have won and/or podiumed almost every race they have been in. The mtn ones use heat-treated drywall channel screws (VERY sharp) and have about 550 per tire. These do not slip no matter how chewed the ice gets. The other set are 700 x32 Vittoria cross tires and use standard sheet metal screws. These are not quite as grippy but are way faster. These have about 500 per tire.