.t-store__parts-switch-btn,
.t-store__parts-switch-btn * {
    font-size: 30px !important;
    line-height: 1.2 !important;
}

@media screen and (max-width: 640px) {
    .t-store__parts-switch-btn,
    .t-store__parts-switch-btn * {
        font-size: 25px !important;
    }
}