Most go through a manual diagnostic process more rigorous than random factory tests. Key components like hard drives, batteries, and RAM are tested and replaced if they don't meet standards.
Visible cosmetic wear like scratches or minor dents, but fully functional. Grade C: Heavier cosmetic wear, but still operational. Top 3 Reasons to Go Refurbished Guide to buying refurbished or second-hand computers buy refurbished computers
To help you manage expectations, many sellers use a grading system: Grade A: Near-mint condition; may have very minor scuffs. Most go through a manual diagnostic process more
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