When sourcing over-extension slides, the most critical factor is the load capacity, which typically ranges from 35kg to over 220kg for heavy-duty industrial applications. You must verify the extension length, as 'over-extension' implies the drawer travels 100% to 120% of the slide length, providing full access to the rear of the drawer. Additionally, prioritize cold-rolled steel with a zinc-plated or electrophoretic black finish to ensure corrosion resistance and structural integrity under repeated cycles.