Regarding the "safe harbor" rule of paying estimated taxes of 110% of last year's tax liability, is last year's tax liability FIT + SS Tax + Medicare Tax?

Spouse is W-2 and I am 1099.  I am trying to figure out  what would be the 110% amount to use for estimated taxes.  Is the base my spouse's FIT only plus my Self Employment tax or is it spouse's FIT, SS, Medicare tax plus my SE tax or is it spouse's FIT only and my FIT only?