When sourcing cabochons, you must prioritize dimensional accuracy and surface finish. Ensure the calibrated sizes (e.g., 10x14mm, 18x25mm) have a tolerance of no more than ±0.2mm to fit standard jewelry settings. The dome height (high, medium, or low) should be consistent across the batch to ensure uniform aesthetics. For the surface, look for a high-gloss polish free of visible scratches, pits, or 'orange peel' textures. Additionally, verify the flatness of the base; a perfectly flat back is essential for secure gluing or bezel setting.