<div class="item">
  
</div>

.item{
  width: 550px;
  height: 300px;
  background: linear-gradient(to right,#0566aa,#051b56);
  border-radius: 4px;
  position: relative;
  margin: 20px;
}

.item::after{
  content: "";
  display: block;
  width: 0;
  border: 10px solid transparent;
  position: absolute;
  right: -20px;
  top: 50%;
  transform: translateY(-50%);
  border-left: 10px solid #051b56;
}