Basketball and soccer.
Basketball jerseys need a clear neckline, armhole, body length, and volume specification, often coordinated with shorts. Soccer jerseys involve their own sleeve, collar, body, and movement requirements. For either category, define whether the product is intended for play, training, fan use, or fashion, because that purpose guides the material and fit conversation.
Provide any applicable team or competition instructions for numbering, colors, sponsor marks, and garment presentation. Those requirements should be reviewed for the actual organization rather than assumed from another sport or league. If performance characteristics are important, state them separately and agree the evidence needed to support the finished product.