Type S Knockout Seals with Screw Bar 2-1/2" - Set screw/bar type knockout seals are inserted in open box knockouts to protect exposed wires.Type S with Screw Bar Knockout Seals 2-1/2" features include: Set screw/bar type knockout seals are inserted in open box knockouts to protect exposed wires Used in standard, air tight or dust tight applications Pre-assembled screw and backer bar slides on open knockout holes without removing box devices or covers Steel Galvanized Order Qty of 1 = 1 Piece Below is more info on our Type S with Screw Bar Knockout Seals 2-1/2"