Didn't take long after the purchase of my PC router that the base included would not do the job.  Standard base would not accept a " round over bit.  I thought about enlarging the hole someway but thought it might leave some burrs that would mark my wood.  New base was the only solution.  The base plate accepts the larger router bits I sometimes use just fine.  The added bonus to the base plate is its clear design.  This is a good plus when using the router as you can precisely get the bit on the wood by eyesight.