8-18 x 3/4 #6HD Unslotted Indented Hex Washer High Low Screw Fully Threaded Zinc MSO188 They have a 3/4-10 thread

They have a 3/4-10 thread size and are 8 inches long

The 1" High Collar Split Lock Washer Plain is a versatile and durable washer designed to prevent nuts and bolts from loosening due to vibration or movement

and the 2/3 thread provides a strong hold

which means they can be easily installed and removed without the need for tools

6-19 x 3/4 6-Lobe Flat High Low Screw Fully Threaded Black Oxide and Oil:

8-18 x 3/4 #6HD Unslotted Indented Hex Washer High Low Screw Fully Threaded Zinc MSO188 They have a 3/4-10 thread#6 x 3 4" #6HD Unslotted Indented Hex Washer High Low Screw Fully Threaded Zinc. A fully threaded, hex washer head screw with an indented hex drive and zinc plating. The screw is designed for use in high low applications, where the head of the screw is countersunk below the surface of the material. The indented hex drive provides a secure grip for driving the screw, and the zinc plating provides corrosion resistance.