.grid {
    margin: 0 auto;
}
.grid-item {
    margin-bottom: 18px;
}
.grid-sizer, .grid-item {
    width: calc(50% - 9px);
}
.grid-item img {
    width: 100%;
    aspect-ratio: 251/348;
    object-fit: cover;
    display: block;
}
.grid-item:nth-child(2n) img {
    aspect-ratio: 251/276;
}

@media only screen and (min-width: 1200px) {
    .grid-sizer, .grid-item {
        width: calc(33.333% - 12px);
    }
}