.tabs__nav { border-bottom: 2px solid #e9e9e9; list-style: none; padding: 0; margin: 0 0 2em 0 !important; } 
.tabs__nav li { display: inline-block; padding: 0; margin:0; position: relative; }
.tabs__nav a { padding: .5em 1em; margin: 0 2px 0 0; background: #ccc; display: block; outline: 0; }

.tabs__nav a::after {
	content: '';
	position: absolute;
	top: 100%;
	margin-left: -16px;
	left: 50%;
	width: 0;
	height: 0;
	overflow: hidden;
	border-left: 12px solid transparent;
	border-right: 12px solid transparent;
	border-top: 8px solid #e9e9e9;
	
	opacity: 0;
	
	transition: opacity .5s;
}

.tabs__nav .ui-tabs-active a { background: #e9e9e9; color: #000; }
.tabs__nav .ui-tabs-active a::after { opacity: 1; }