Protective helmets are classified according to the specific impact and electrical performance requirements they are designed to meet. All protective helmets in accordance with this standard shall meet either type I or type II impact requirements. In addition, all helmets are further classified as meeting class G, class E, or class C electrical requirements. Slotted, impact absorbing design. Universal slot for attaching additional protection options. Deep nape strap and absorbent cloth sweatband for a comfortable fit. Chin straps are available for all models.