People who like ufc and who know clothing sizes!!!!!!!!!!!!!?

i want to buy the dark side shirt but i am a large youth and i was thinking if i could fit in a small or medium adult please help really want the shirt this is what it looks like----------a href="http://cgi.ebay.com/NEW-TAPOUT-T-SHIRT-MMA-darkside-MENS-SHIRT-S_W0QQitemZ280312770591QQcmdZViewItemQQptZUS_CSA_MC_Shirts?hash=item280312770591&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A0%7C293%3A1%7C294%3A50" rel="nofollow"http://cgi.ebay.com/NEW-TAPOUT-T-SHIRT-M…/a