Youth XL is about a between a medium-small u get in Australia.
Here is a sizing Chart
Adult Sizing - NBA Jersey Sizing (Swingman) Reebok
Small Med Large XL 2X 3X
Chest 40" 44" 48" 52" 56" 60"
Length 33" 34" 35" 36" 37" 38"
Youth Sizing - NBA Jersey (Youth) - Reebok
YOUTH Small Med Large...