When sourcing street shirts, the fabric weight (GSM) is the most critical indicator of quality. For a premium 'streetwear' feel, look for heavyweight cotton (240-300 GSM), while standard retail shirts typically range from 160-200 GSM. Ensure the material is 100% combed cotton or a cotton-polyester blend for better shape retention. Additionally, verify the colorfastness rating (Grade 4 or higher) to ensure the shirts do not fade after multiple washes, which is a common requirement for high-end streetwear brands.