adidas + F50.6 Tunit Cleat Kit Synthetic micro fiber upper with covered lacing to provide a larger and more consistent kicking area Comfort chassis included Stud Key and three sets of studs for soft, firm or hard ground playing surfaces Soft Ground (aluminum) -- two 16mm heel studs with two blind studs and six 13mm forefoot studs Firm Ground (thermoplastic polyurethane) -- four 13mm heel studs and six 11mm forefoot studs