This is only an option on our fence extension arms. In terms of which material to use, most dogs are fine with the plastic (standard). The only people who really need to consider the welded wire (heavy duty) option are those folks whose dogs might be inclined to try to get a mouthful of the material and hang from the fence. The plastic fence is very strong and great for impact but point loads on the joints like those applied with a dog's tooth can snap the joint and make a hole.