.set_5_button {
    background: #fff;
    color: #666;
    overflow: hidden;
    z-index: 1;
    float: left;
    font-weight: 400;
    line-height: 45px;
    margin-right: 2.5em;
    cursor: pointer;
    overflow: hidden;
    /* padding: 0 25px; */
    position: relative;
    /* text-align: center; */
    width: 100%;
    /*border: 1px solid #ccc; */
}

.set_5_button:before {
    content: "";
    display: block;
    position: absolute;
    left: 0;
    top: 0;
    width: 0px;
    background-color: #000;
    opacity: 0.1;
    height: 50px;
    /* transition: width .3s;
    -moz-transition: width .3s;
    -webkit-transition: width .3s;
    -o-transition: width .3s; */
}


.set_5_button:hover::before {
    width: 100%;
}