Mesh opening size directly determines what can be loaded without leaking and what stays visible; it is measured by center-to-center spacing of adjacent wires, commonly between 25mm and 100mm. The combination of wire diameter and mesh opening gives the actual opening size of the mesh.
For small parts, loose materials, or fasteners like bolts and nuts, choose a small mesh opening—below 50mm or even denser—to prevent leakage; for large items, turnover boxes, and packaged goods, the opening can be 80mm or more, saving material, reducing self-weight, and making visual counting easier.
Mesh opening also affects overall rigidity: the denser the mesh, the more evenly stress is distributed, and the less the mesh surface bulges or deforms; if you widen the opening but still need to hold fine materials, you often have to compensate by thickening the wire or adding liner plates, which costs more. When selecting, think through "what is loaded now and what might be loaded later."
Before deciding the opening, measure the outer dimensions of the smallest item and leave adequate clearance; in scenarios with many fine materials, consider denser mesh or a pad at the bottom while keeping larger openings on the sides, balancing leak prevention, ventilation, and appearance.
Practical advice: tell the manufacturer the smallest-item size, single-item weight, and visual counting needs together, and let them propose a wire-diameter-plus-opening combination; sample-load a batch of real materials to verify no leakage before mass production. You can also do a trial load before production, putting several typical materials into the sample cage and shaking it to confirm nothing falls through the openings, then finalize the mesh spec.