Knockout plugs for distribution boxes typically range from $0.20 to $5 per piece, depending on material, size, and quantity.

Overview of Knockout Plugs

Knockout plugs are used to seal unused holes in electrical enclosures, protecting wiring from dust, moisture, and debris. They come in metal or plastic, with sizes commonly ranging from ½ inch to 1½ inches or metric equivalents like M12, M16, M20, and M32 . Plastic plugs are often made of Nylon 6/6, resistant to oil, heat, and corrosion, while metal plugs are typically galvanized steel .

Price Ranges

• Plastic Knockout Plugs: Small sizes (M12–M20) generally cost $0.20–$1 per piece, with bulk packs reducing the per-unit cost .
• Metal Knockout Plugs: Standard ½ inch to ¾ inch galvanized steel plugs are priced around $1–$5 per piece, depending on brand and quantity .
• Bulk Packs: Some suppliers offer packs of 50–120 plugs, which can lower the cost to $0.15–$0.50 per plug .

Suppliers and Options

• Amazon: Offers a wide range of metal and plastic knockout plugs, with prices varying by size and pack quantity .
• McMaster-Carr: Provides individual plugs and fittings with same-day delivery, suitable for industrial or commercial use .
• Polycase: Specializes in plastic threaded plugs with waterproof seals, ideal for NEMA-rated enclosures .

Considerations

• Material: Choose metal for durability and grounding, plastic for corrosion resistance and cost savings.
• Size: Ensure the plug matches the knockout diameter of your distribution box.
• Quantity: Buying in bulk reduces per-unit cost.
• Sealing Requirements: For outdoor or wet environments, select plugs with integrated sealing rings or waterproof ratings .

By selecting the appropriate material, size, and quantity, you can budget effectively for sealing unused knockout holes in distribution boxes.