IGrip SS18 Shoulder Tire Studs - 18mm (Qty: 150) SS-18150For many years iGRIP has offered ST type (standard tread) studs. However, in order to improve the product range, iGRIP has added two stud types to the stock, thus answering to the customers needs. The SS (shoulder studs) models were designed for heavy machinery and all kinds of vehicles used in extreme conditions and environments. As well, there are SF (spark free) model studs, which, as the name suggests, do not create sparks when in contact with the