The Unique Features of Aktion Safety Helmets : Penetration Test, Water Absorption, Shock Absorption, Rain gutter, Electrical Resistance, Flammability Resistance, Heat Resistance Nap Type, 4 points tectonic harness, Can be used with earmuff, Flexible comfort chin strap, Aktion Safety Helmet with Nap strap an I.S.I., 2925. Certified. HDPE Universal slots for ear protectors. Air ventilators unique breath freely design comfortable to wear for long time. Highly absorbent sweatband allows good absorption and does cause skin reaction. Available in both ratchet type and manual adjustment.