Vintage Don Alleson all nylon gym shorts. They feature white trim at the leg openings and sides and an elastic waistband. 
These shorts are bright, clean, free of tears, stains. These are sized to fit a youth size large.  See measurements below.

Measurements:
Tag size: Large
12" Out seam
3 1/2" Inseam
12" Waist (one side, flat, unstretched. Can be stretched to 13", one side.)
Fabric content: all nylon