1000pcs Compression Spring A2 304 Stainless Steel Pressure Springs 0.4x3x10mm

The three numbers refer to wire diameter × outer diameter × free length. So 0.4x3x10mm means a 0.4 mm wire, 3 mm outer diameter, and 10 mm uncompressed length. Always match all three dimensions to your application's bore, shaft, and travel requirements.

304 stainless steel offers a good balance of tensile strength and corrosion resistance for light-to-medium load applications. For very high-cycle fatigue or heavy-load environments, consider music wire or 316 stainless alternatives. For electronics contacts, pen mechanisms, and small actuators, 304 is well-suited.

A2-grade 304 stainless steel provides solid resistance to oxidation and moisture in most indoor and light outdoor environments. It is not recommended for prolonged exposure to chloride-rich environments (e.g., saltwater or pool chemicals) without additional protection.

These springs are commonly used in battery contacts, push-button switches, pen and stylus mechanisms, miniature latches, sensor housings, small robotics actuators, and any assembly requiring a 3 mm OD spring with 10 mm free length. Verify your bore diameter accommodates a 3 mm OD with appropriate clearance.

Match the outer diameter to your bore (OD should be slightly smaller than the bore), the inner diameter to your shaft (ID should be slightly larger than the shaft), and the free length to your available travel plus compressed length. The wire diameter determines the spring rate — thicker wire = stiffer spring.

Small compression springs are easy to lose during assembly and often needed in multiples per unit. A 1000-piece pack is cost-effective for prototyping batches, small production runs, or maintaining a workshop stock so you are never blocked waiting for a reorder.

304 stainless steel maintains its mechanical properties from approximately −40 °C to +300 °C (−40 °F to +572 °F). For applications exceeding this range, consult a spring engineer for high-temperature alloy alternatives.