Morris 22398 Plastic Knockout Plug, 1-1/2-Inch, Black, 10-Pack Plastic Knockout Plugs - Snap-In - Our Plastic Knockout Plugs - Snap-In are low-cost and easy to use. Plastic Knockout Plugs - Snap-In plugs electrical knockouts with finger tip pressure Low cost and assure good appearance Snap-In winged protrusion for Positive Lock Less costly & safer than steel snap-in blanks