#single-prod-gallery li:not(.flex-nav-next):not(.flex-nav-prev) {
    background-image: url(https://dev.bardahladditivi.it/wp-content/uploads/2024/08/benzina-fondo-additivi-maroil-bardahl-italia.webp);
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
}