I bought a PDI 6.05 554mm barrel from Xfire two weeks ago, cost me £56 as opposed to £96 in the UK, I was lucky and didn't get hit with a customs charge. Idealy you want a 430mm barrel to fit your VSR Pro, 6.03 is a quality size although 6.05 is also popular! I have a 6.01 edgi barrel in mine and it prefers .4's over .43+.