The "1-1/4"-7" designation specifies that the nut is designed to mate with a bolt or rod that has a thread size of 1-1/4 inches in diameter with 7 threads per inch.
Material:
These nuts are typically made of low-carbon steel, often with a zinc coating for corrosion resistance.
Application:
Slotted nuts are used in applications where vibration or motion might cause the nut to loosen, such as in machinery, automotive, or construction where a secure fastening is essential.