Marine screws are locked in place thanks to their "teeth" (the thread indentations will resist back-out even after prolonged vibration)

High-strength alloy clip on carbon-steel anchors: This special alloy clip offers improved performance

These are premium quality

3/8-16 x 1 1/2 Grade 8 Hex Cap Screw Plain Domestic USA (675)

3/8-24 x 1 3/4 Grade 5 Hex Cap Screw Plain Domestic USA (100)

5/16-18 x 3 1/4 Grade 5 Hex Cap Screw Zinc Plated Domestic USA (50) Phillips Flat Particle Board Screws T17 Black Oxide Marine screws are locked in5 16 18 x 3 1 4 Grade 5 Hex Cap Screw Zinc Plated Domestic USA (50) . Grade 5 Hex Cap Screws are manufactured in the USA from medium carbon steel. Our Grade 5 material meets or exceeds SAE J429 Grade 5 specifications. All products are manufactured with rolled threads. Typical hardness on diameters 1 4 to 1 inch is HRC 25 34. On diameters over 1 inch to 1 1 2 hardness will range from HRC 19 30. Tensile strength for diameters 1 4 to 1 inch is a minimum