• Here are a few options
• all suitable for South American Spanish
• with slight variations in wording: **Option 1 (Most common and direct):** "Algunas marcas negras tenues en la parte superior delantera
• una pequeña marca en la parte trasera." **Option 2 (Slightly more formal for "marks" as "stains"):** "Algunas manchas negras tenues en la parte superior frontal
• una pequeña marca en el reverso." **Option 3 (Concise):** "Leves marcas negras en la parte superior frontal
• una pequeña marca en la espalda." **Breakdown of terms:** * **Faint black marks:** * *Marcas negras tenues* (faint black marks - most direct) * *Manchas negras tenues* (faint black stains/spots - if they are more like stains) * *Leves marcas negras* (slight/light black marks) * **Upper front:** * *Parte superior delantera* (upper front part) * *Parte superior frontal* (upper frontal part) * **Small mark:** * *Una pequeña marca* (a small mark) * **Reverse:** * *Parte trasera* (back part - very common for clothing) * *Reverso* (reverse - also common) * *Espalda* (back - refers to the back of the garment
• like the back of a person) I'd recommend **Option 1** as it's very clear and natural.

Características:

• Etiquetas oficiales y originales de Adidas
• Manga larga