Wire-core fliplines are made with braided arborist rope over steel cable. This gives a Wire-core flipline extra rigidity, making it easier to flip up the tree - especially on larger stems. A running chainsaw will easily sever a Wire-core flipline; and they should not be considered chainsaw-proof. Caution must always be used in the tree.
Wire-core fliplines are available in diameters from 7/16" to 3/4". Larger diameters can be easier to grip but also add to the weight and bulk of your climbing kit.