.flex-images .item {
    border: 1px solid #eee;
    box-sizing: content-box;
    float: left;
    margin: 4px;
    min-width: 1px;
    min-height: 1px;
    overflow: hidden;
    position: relative;
}

    .flex-images .item img {
        display: block;
        height: 100%;
        width: auto;
    }