<div class="wrapper-inactive"><div class="tab"><a href="#">Tab 1</a></div></div>
<div class="wrapper-inactive"><div class="tab"><a href="#">Tab 2</a></div></div>
<div class="wrapper-active"><div class="tab"><a href="#">Tab 3 (Active)</a></div></div>
<div class="wrapper-inactive"><div class="tab"><a href="#">Tab 4</a></div></div>
<div class="wrapper-inactive"><div class="tab"><a href="#">Tab 5</a></div></div>
.wrapper-active, .wrapper-inactive {
  width: 120px;
  height: 80px;
  display: inline-block;
}

.wrapper-active {
  position: relative;
  z-index: 1;
}

.wrapper-active > .tab {
  background: #8671ed;
}

.tab {
  float: left;
  border: 5px solid black;
  text-align: center;
  background: #c5bbf7;
  position: relative;
  width: 100%;
}

.tab:after {
  position: absolute;
  top: -5px; 
  left: 12px;
  transform: skewX(20deg);
  transform-origin: 100%;
  content: '';
  z-index: -1;
  height: 100%;
  width: 100%;
  background: #342c59;
  border: 5px solid black;
}

a {
  line-height: 80px;
}
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