I guess you are probably inquireing about forged cranks but most of my experiance has been with their cheaper stuff, one was a cast 4in crank SB with no mods except the crank and pistons, it was just thrown in during a rebuild to get a little extra towing power even had a stock cam and heads intake and it broke between the number one rod and main, the factory ground away so much material to lighten it up (so it could internal balance accordin to them)but than nothing was left to hold the crank together AND there was a bubble in the casting in there, it broke just a couple weeks after instalation. Absolutley no excuse for that! Also I have seen the SIR rods break in low power motors, the beam just pulled apart right on the factory installed stress risers

Because they make such total crap on the bottom end of the scale I won't use any of their stuff, of course the machining is no where as good as SCAT and K1 on the better stuff for the same price.