.b-stylem5-en {
    width: 100%;
}

@media screen and (min-width: 768px) {
    .banner_img {
        height: 200px;
        background: url(http://images.peaksonic.com.cn/images/product/banner_m5_en.jpg) no-repeat 0 0;
        background-size: 100%;
    }
}

@media screen and (min-width: 1200px) {
    .banner_img {
        height: 360px;
        background: url(http://images.peaksonic.com.cn/images/product/banner_m5_en.jpg) no-repeat 0 0;
        background-size: 100%;
    }
}

@media screen and (min-width: 1900px) {
    .banner_img {
        height: 450px;
        background: url(http://images.peaksonic.com.cn/images/product/banner_m5_en.jpg) no-repeat 0 0;
        background-size: 100%;
    }
}

@media screen and (max-width: 768px) {
    .banner_img {
        height: 190px;
        background: url(http://images.peaksonic.com.cn/images/product/banner_m5_small.jpg) no-repeat 0 0;
        background-size: 100%;
    }
}