PDI 6.03mm precision barrels are made of cold hammer forged SUS304 stainless steel. They are among the highest quality barrels available for airsoft. They are made in Japan with extremely tight bore tolerances of +- 0.002mm.
For those looking to split the difference between 6.01mm and 6.05mm barrels.
For AEG / Tokyo Marui TM AEG.
Inner Diameter: 6.03mm
Outer Diameter: 8.55mm
Made of cold hammer forged SUS304 Steel