.icon-stack, .icon-stack-ib {
    position: relative;
    width: 2em;
    height: 5em;
    line-height: 4em;
    vertical-align: middle;
}

.icon-stack-ib { display: inline-block; }

.icon-stack-xs,
.icon-stack-1x,
.icon-stack-2x,
.icon-stack-3x {
    position: absolute;
    left: 0;
    width: 100%;
}

.icon-stack-xs {
    line-height: inherit;
    position: absolute;
    left:15px;
    top:-14px;     
}

.icon-stack-1x {
    line-height: inherit;
    position: absolute;
    left:14px;
    top:-14px;
}

.icon-stack-xs {
    font-size: 0.8em;
}

.icon-stack-xs {
    font-size: 1.1em;
}

.icon-stack-2x {
    font-size: 1.5em;
}
.icon-stack-3x {
    font-size: 2em;
}