Stainless steel. Ideal for securing seat pedestal bases or stanchions to decks or any type of accessory to cabin walls. Fast and easy to install. Can be used in any thickness deck or cabin wall from 3/8" to 2-1/2". Requires only a 1/2" hole. Stays in place without bolt and will not spin during installation. Allows bolt removal without losing anchor under deck or behind cabin wall. Metal to metal installation insures maximum strength. Made of 304 stainless steel.