Mizuno Mesh Sliding Pants 140

My son was very sensitive, so he only tried these on and kept them stored without wearing them. Because of this, they are in very good condition. When I took them out after a long time, I noticed some faint stains, so I washed them again, but they didn't come out. *Please refer to the 4th photo.
The size 140 feels quite small.
We are looking for buyers who understand this.
How about these for a child who is just starting baseball?

{Product Description}
Mesh material white sliding pants with padding for a comfortable fit.

- Brand: Mizuno
- Size: 140
- Color: White
- Design: Mesh material
- Features: Padded
- Waistband: With logo

Thank you for looking.

Size...XS (SS)
Mizuno
Sliding pants
Kids
Children
Youth baseball
White