Square shaped shims and round shims are two common fasteners, mainly used for connecting the gap and stress distribution between bolts, nuts and connecting parts to reduce friction, limit deformation, transfer pressure and prevent air and liquid leakage.

• Shape: Square shims are in quadrilateral shape with equal side lengths and 90-degree angles; round shims are round with uniform circumferential edges.
• Application scenarios: Square shims are suitable for certain square or regular structural connections and bolt holes due to their shape characteristics, mainly used for track connections such as angles, I-beams and rails; round shims are suitable for a wide range of scenarios and are more commonly used.
• Material: Both can use various metal and non-metallic materials (steel, copper, aluminium, rubber, silicone, etc.), selected based on working conditions.
• Installation effect: Round gasket edges provide continuous circumference with more uniform stress distribution; square gaskets may have force concentration at corners.
• Torque control: Generally easier with round shims due to uniform pressure distribution; square shims may require stricter torque control to avoid corner overloading.
• Stress concentration: Square shims have four corners where stress may concentrate, while round shims distribute stress more evenly.

Flat washers are thin, flat, round with a hole in the center. The flat washer application is designed to apply loads over a relatively large area and provide support for small head screws. Also known as A-flat washers, they are suitable for general use.

• High strength: Excellent strength characteristics suitable for construction, automotive, and aerospace applications.
• Good wear resistance: Ideal for tools, machine parts and industrial equipment.
• Strong plasticity: Easy to process and form into complex shapes through cold working, hot working and forging.
• Price economy: Competitive cost advantage for large-scale industrial applications.

• Corrosion tendency: Requires corrosion protection or resistant coatings when exposed to moisture or acidic substances.
• Low shock resistance: Less suitable for vibration environments compared to high-strength alloys.

Galvanizing is a surface treatment technique of plating a layer of zinc on the surface of metals, alloys or other materials to provide a beautiful and rust-resistant appearance. The color of zinc after galvanizing is silver-white, and the color after passivation of galvanizing can be white, colored, army green, etc.