Question about scuba tank And oppinion on Crossfire tanks??

[MAGS_R_COOL]

I would get a 4500. If you go to a a field that gives 4500 fills you wont be left in the dark. And plus...if you only fill your 4500 tank w/ 3k, it will perform just as good as a 68/3k. And you are using a mag...so I would go with a 68/45. I shoot one on a uni-mount and it is set up PERFECTLY.
Im definately glad about my choice of tank.