Mutual Fund Fees/Expenses?

I was wondering what the difference was between Class A and Class I shares, when it comes to mutual fund shareholders.  The fees are different for the two, and I was curious which one I am classified as.  I hold various funds through my 401K.  Thanks in advance, guys.

 

 

Class A are usually bought with a sales charge up front.  Sales charge can vary depending on Fund itself and amount being invested.  Within a 401k there may or may not have a sales charge depending on the fund family....say if aggregate amount of assets are over a certain dollar amount.  The I shares may be something specific to institutional accounts or something...some families use R shares.  Not really sure about the I's though.