Beyond the alloy grade, focus on grain structure and homogenization. High-quality billets must undergo a homogenization heat treatment to ensure a uniform distribution of alloying elements, which prevents tearing during extrusion. Specify the diameter tolerance (typically ±1% or less) and straightness to avoid feeding issues in the extrusion press. Additionally, ensure the billets are free from surface defects like scales, cracks, or inclusions, as these will translate into flaws in the final profile.