303, 304, 316L or 904?
Start from the application.

Technical review by the Zhenglong manufacturing team, Dongguan · Updated November 2026

Stainless steel grade affects raw-material availability, corrosion resistance, machining behavior, finish and cost. The correct choice must come from the product's environment and engineering requirements, not from the assumption that a higher alloy grade is automatically better.

1. Quick sourcing comparison

2. When buyers specify 303 or 304

303 is generally selected for parts where machinability is a priority and the application permits a free-machining austenitic grade. It can be relevant to repeat turned parts and small hardware, but the exact alloy and any restriction on sulfur-bearing grades must be confirmed for the application.

304 is common in general industrial and consumer hardware where a combination of corrosion resistance, clean appearance and broad availability is needed. It can suit watch-related parts, decorative components and non-standard hardware when the operating environment permits.

The RFQ should still state the exact grade standard, surface condition and finish. A generic request for "stainless" leaves material and commercial assumptions unresolved.

3. When buyers specify 316 or 316L

316 is often selected when the application requires improved corrosion resistance compared with 304, particularly where chloride exposure is a concern. 316L is the low-carbon variant and may be specified where the drawing or application calls for it. The final suitability still depends on the exact medium, temperature, cleaning process, design and service conditions.

The liquid-cooling component photographed on this website is confirmed as 316 stainless steel and includes multiple machined ports and internal threads. That example confirms material and application only. It does not establish a pressure rating, coolant compatibility, leakage performance or system-level approval for another project.

4. When buyers specify 904-series

904-series stainless steel is a higher-alloy austenitic group reviewed when the product specification calls for more demanding corrosion performance or a particular premium-material requirement. The exact grade, such as 904, 904L or another designation, must be stated in the drawing and confirmed in the RFQ; do not treat the series name as a single interchangeable specification.

This material is typically more expensive and less broadly stocked than 304 or 316, so exact grade, quantity, material record and documentation should be confirmed early.

For high-appearance products such as watch cases and luxury hardware, material selection may also be tied to polishing, brushing, PVD or other finish requirements. The approved appearance should be defined separately from the grade name.

5. Questions that affect machining

Austenitic stainless steels can work-harden, generate heat and require controlled tools and cutting conditions. For sourcing purposes, the most useful information is the geometry and performance requirement that the process must achieve.

• Deep holes, thin walls or interrupted cuts
• Multiple threaded ports and cross-hole relationships
• Tight bores, sealing faces and mating dimensions
• Sharp edge restrictions and deburring requirements
• Dimensions that apply before or after surface treatment
• Prototype quantity and expected repeat batch

6. Define surface and appearance separately

Material grade does not fully define the finished appearance. State whether the part is as-machined, polished, brushed, sandblasted, PVD coated, electroplated, engraved or otherwise treated. Machining and inspection are handled in our Dongguan workshop; polishing, brushing, blasting and engraving can be completed in-house, while PVD, plating and stone setting are coordinated with qualified finishing partners where required.

For functional interfaces, identify surface roughness, coating restrictions and any features that must remain protected during finishing.

7. Stainless steel RFQ checklist