styling Grid Header

Hello,
In my project I'm using the grid Component with this style
.easyship .v-grid-header .v-grid-row .v-grid-cell{
    height: 35px;
    font-size: 15px;
    color: black;
    font-weight: 800;
}
but I have a page where I want to use the Grid with another style 
.easyship .v-grid-header .v-grid-row .v-grid-cell.twolinesheader {
    height: 60px;
    white-space:normal;
}
I tried m_oGrid.setStyleName("twolinesheader") but the first style is used .How can I achieve to use the second style (twolinesheader) for my grid ?
Thank you
 

You seem to have defined the other style as the subclass of the first one (the dot syntax in the name), so then it naturally inherits the stuff you defined. Instead you should define unique style name to each of the Grid's you use.
 

I tied also with 
.twolinesheader {
    height: 60px;
    white-space:normal;
}

but the same result