.header .mod-menu > li {
  position: relative;
}

.header .mod-menu li:hover > ul {
  background-color: #fff;
  border: 1px solid #dfe3e7;  
  border-radius: 5px;
  display: block;
  position: absolute;
  top: 100%;
  left: 0;
  min-width: 250px;
  padding: 16px;
}

.header .mod-menu li:hover > ul li {
  display: block;
}