Here's a size Youth XL (Steve & Barrys 90% Cotton 10% Polyester) E=MC2 T Shirt....(measures approx. 19 across by 26 length)......screened graphics on front....shirt is pre-owned and in very good shape overall,..........In physics, mass–energy equivalence is the relationship between mass and energy in a system’s rest frame, where the two values differ only by a constant and the units of measurement. The principle is described by the physicist Albert Einstein's famous formula: Formula: 
Name: mass–energy equivalence
Description: physical law relating mass to energy