The material by high-strength, low-alloy weathering steel, the size is from 3/8 to 1-1/4".
Self Tapping Screw, are most often used to fasten sheet metal composite materials, woods and plastics. They have a high tensile strength value, and are durable enough to handle repeated assembly and disassembly.
Most screws are available with painted heads, protective coatings and bonded washers to order.