It sounds like you're describing a versatile and durable T-shirt made from 100% cotton that has undergone a bio-wash treatment. This treatment is often used to soften the fabric and improve its color retention.

Given that it's available in 10+ colors and designed to fit children from 1/2 years old to 9/10 years old, it seems like a practical and adaptable clothing option for parents looking for long-lasting wear for their children.

Here are some potential features and benefits of such a T-shirt:

1. Comfort: Cotton is known for its comfort and breathability, making it suitable for everyday wear for kids.
2. Durability: Bio-washed cotton tends to be more durable and less prone to shrinkage compared to untreated cotton.
3. Versatility: With a range of colors available, parents and children can choose according to personal preference or to match different outfits.
4. Longevity: The fact that it's designed to fit children over several years means it offers good value for money and reduces the need for frequent replacements as children grow.

Overall, this type of T-shirt seems like a practical choice for parents seeking quality, longevity, and comfort for their children's clothing needs.