<prompt> Human: Hey PF,I just started a new job recently and have begun setting up my 401k investments. One thing I noticed is that most of the funds offered through the 401k have fairly high expense ratios 0.5-1.09, although 1 SP 500 index fund is offered, at a very reasonable expense ratio of 0.04.What I started thinking about doing was putting 100 of my 401k contributions into that SP 500 index fund, and then simultaneously setting up an IRA, where I can have more options and contribute almost exclusively towards the International Stock Index Fund and the Total Bond Market Index Fund to increase diversification. My goal is to basically create a form of the Three-Fund portfolio at the lowest ERs possible.So my question is - is there any cons to this strategy? I imagine that maintaining my asset allocation could get tricky, but is there any challenges or risks that I am just not seeing or considering?  <response>: I see no problem in what you are doing and follow a similar strategy.Between my Roth IRA, 401k, and HSA i keep them balanced focusing on expense ratio. HSA only had low expense for SP 500 so its 100 there. 401k has low bonds, so its heavy in that 20 here to get me to 10 overall. Roth IRA I plug differences because the choices are boundless. 