bootstrap/site/docs/4.1/examples/checkout/form-validation.css

.container {
  max-width: 960px;
}

.border-top { border-top: 1px solid #e5e5e5; }
.border-bottom { border-bottom: 1px solid #e5e5e5; }
.border-top-gray { border-top-color: #adb5bd; }

.lh-condensed { line-height: 1.25; }