@media only screen and (max-width: 600px) {
    lbl-tx-size {
        font-size: xx-small;
    }
    /* For mobile phones: */
    [class*="col-"] {
        width: 100%;
    }
}
@media (min-width: 768px) {
    lbl-tx-size {
        font-size:xx-large;
    }
}