.jarallax {
    position: relative;
    z-index: 0;
}

    .jarallax > .jarallax-img {
        position: absolute;
        object-fit: cover;
        /* support for plugin https://github.com/bfred-it/object-fit-images */
        font-family: 'object-fit: cover;';
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        z-index: -1;
    }