@media only screen and (max-width: 1023px) {
    .stm_mobile__dropdown:after {
        content: '';
        display: block;
        position: absolute;
        top: 50%;
        left: 50%;
        width: 0;
        height: 0;
        border-style: solid;
        border-width: 5px 3.5px 0 3.5px;
        border-color: #aaa transparent transparent transparent;
    }
}