A SKU (Stock Keeping Unit) is a unique identifier for a product in a specific configuration — size, color, variant. Two versions of the same product that differ in size are different SKUs, even if they have the same manufacturer part number.
A clean SKU system uses a consistent naming convention: product code, variant code, and channel code. For example, SHIRT-BLU-L-FBA identifies a blue large shirt destined for FBA. Consistency prevents errors at the prep center.
Keep SKU count as low as possible. Each additional SKU adds receiving complexity, prep tracking burden, and inventory management overhead. Products with many color and size variants should have a clear system before inventory starts flowing.
Share your SKU master list with your 3PL and keep it current. A prep center working from an outdated SKU list will either reject shipments with new SKUs or worse — prep them incorrectly under an old label.