Nylon 6:

Pros: Good balance of strength, stiffness, and abrasion resistance. Relatively low cost.
Cons: Lower temperature resistance than some other nylons. Susceptible to UV degradation.
Common uses: Gears, bearings, fibers, textiles, clothing, ropes, and automotive parts.

Nylon 66:

Pros: Higher strength, stiffness, and temperature resistance than Nylon 6. Excellent abrasion resistance.
Cons: More expensive than Nylon 6.
Common uses: Gears, bearings, electrical components, medical devices, and high-performance fabrics.

Nylon 11:

Pros: Excellent chemical resistance, low moisture absorption, and good biocompatibility.
Cons: Lower strength and stiffness than Nylon 6 and 66.
Common uses: Fuel lines, tubing, medical devices, and food contact applications.

Nylon 12:

Pros: Excellent low-temperature flexibility, good chemical resistance, and low moisture absorption.
Cons: Lower strength and stiffness than Nylon 6 and 66.
Common uses: Fuel lines, hoses, and outdoor applications.

Glass-filled Nylon:

Pros: Increased strength, stiffness, and dimensional stability compared to unfilled nylon.
Cons: Higher cost and lower impact resistance than unfilled nylon.
Common uses: Gears, bearings, and structural components requiring high strength and stiffness.

Mineral-filled Nylon:

Pros: Improved wear resistance and heat resistance compared to unfilled nylon.
Cons: Higher cost and lower impact resistance than unfilled nylon.
Common uses: Bearings, gears, and components exposed to wear and heat.

Cast Nylon:

Pros: Excellent machinability, good wear resistance, and low noise generation.
Cons: Lower strength and stiffness than extruded nylon.
Common uses: Gears, bearings, wear pads, and rollers.

Extruded Nylon:

Pros: High strength and stiffness, good dimensional stability, and good chemical resistance.
Cons: More difficult to machine than cast nylon.
Common uses: Structural components, gears, bearings, and pipes.

These are just a few examples of the many different nylon variants and models available. The best choice for your application will depend on the specific properties you need. It is important to consult with a materials engineer or other expert to select the right nylon for your needs.