The Tempress Helm Seat Reinforcement Mounting Plate can be used with all Tempress Elite Helm and ProBax Captain Seats or with any roto-molded style seat requiring support. This high-density polyethylene reinforcement plate ensures bottom reinforcement when installing the Tempress Helm or ProBax Captain Seats to a standard 4-hole mount swivel base. Hardware is not included.• Dimensions: 13" x 7-1/4" x 7/16" thick High-density polyethylene plate ensures seat bottom reinforcement Hardware is not included Measures 13"" x 7-1/4"" x 7/16"" thick