These are the strings that Justin uses on his Acoustic guitars. He uses these on his string changing video 

EXP19 strings are a D'Addario original hybrid gauge and a comfortable compromise for players who want the depth and projection of light gauge bottom strings, but slightly less tension on the high strings for easy bending.

• A D'Addario hybrid gauge, combining light gauge bottom strings with lighter top strings for easy bending
• EXP Coated phosphor bronze for warm, bright, well balanced acoustic tone and 4 times more life
• Feature D’Addario’s exclusive New York manufactured, high carbon steel for unprecedented strength and pitch stability.
• Environmentally friendly, corrosion resistant packaging for strings that are always fresh
• String Gauges: Plain Steel .012, .016, Phosphor Bronze Wound .025, .035, .045, .056