This Nirvana Serpent t-shirt is officially licensed and manufactured by Merch Traffic. The front is screen printed on a silver t-shirt made from 100% cotton.  No design is on the back.

Size,          Brand,        Armpit to Armpit, Top to Bottom
Medium     Nirvana                 19.5"                29.5"
Large        Nirvana                  21"                  31"
X-Large     M & O Gold           23"                  32"
2X-Large   Nirvana                 25"                  33"