Menu separators

Would like to add vertical line separators in between non-Mobile, top level menu items. Am thinking about something like this, but not sure which class to modify…?:

#access ul.menu > li a {
display: inline-block;
vertical-align: middle;
}

ul.menu > li:after {
content: “|”;
font-size: 0.9em;
}

ul.menu > li:last-child:after {
display: none;
}