Hex Slotted Nuts
Product Model:

The difference between Slotted Hex Nut& Castle Hex Nut:
These two nuts look a lot alike. But the difference is at the top. Slotted nuts have flat tops with the full hex across it. The slots in Castle nuts are cut into an upper cylindrical portion that is equal in length to the slot depth – and slightly smaller in diameter than the hex width.

Slotted and castle nuts can be used interchangeably but slotted have become preferred and more commonly used in recent years. 

Types: Hex Slotted Nut
Material: Carbon Steel, Alloy Steel, Stainless Steel, Brass
Grade: SAE J995 Gr.2, 5,8; CL4, 5, 6, 8, 10, 12 / ASTM A563 Gr. A; SAE J995 Gr.2
Thread: M, UNC, UNF
Finish: Plain, Zinc Plated(Clear/Blue/Yellow/Black), Black oxide, Nickel, Chrome, H.D.G
Packing: Bulk in cartons (25kg Max.) + wooden pallets or according to customer demand.
Application: Structural steel industry, Metal building industry, Mechanical equipment industry,
Automobile industry, etc.