#gas {
    display: flex;
    justify-content: center;
    /* Ensure the container doesn't force a height if the ad fails to load */
    min-height: 50px; 
}

/* 1. Mobile (Default) */
#gas > ins { 
    width: 320px !important; 
    height: 100px !important; 
    display: block !important;
    margin: 0 auto !important;
}

/* 2. Large Tablets / Horizontal */
@media(min-width: 600px) {
    #gas > ins { 
        width: 468px !important; 
        height: 60px !important; 
    }
}

/* 3. Desktop Sidebar (flex-gt-md="20") */
@media(min-width: 960px) {
    #gas > ins { 
        width: 300px !important; 
        height: 600px !important; 
    }
}