.grid-sizer,
.grid-item { width: 22%; }
.grid-item { margin-bottom: 10px; }
.gutter-sizer { width: 4%; }

@media (max-width: 1280px) {
  .grid-sizer, .grid-item {
    width: 30%;
  }
}

@media (max-width: 960px) {
  .grid-sizer, .grid-item {
    width: 48%;
  }
}

@media (max-width: 600px) {
  .grid-sizer, .grid-item {
    width: 99%;
  }
}