The Alpha Aggressive features an extremely durable Vibram outsole for superior traction for any outdoor condition. Longwearing, comfortable, lightweight and 100% waterproof, the boots are made with Alpha construction, which consists of ozone-resistant rubber over 3.5mm naturally-insulating neoprene to keep feet dry and comfortable. The steel toe meets or exceeds ASTM standard F2413-05 M I/75 C/75 EH and the rubber upper offers chemical resistance against 26 industry chemicals tested to ASTM F903 Procedure A. A removable EVA footbed provides increased cushioning comfort. A back adjustable gusset allows for varying calf sizes. Fiberglass shank.