SOURCE

    <div class="box"></div>

.box {
    display: flex;
    justify-content: space-between;
    width: 100px;
    height: 30px;
    background-color: blue;
    margin-left: 100px;
    border-top-left-radius: 5px;
    border-top-right-radius: 5px;
}

.box::before,
.box::after {
    margin-top: 10px;
    content: '';
    display: block;
    height: 20px;
    width: 20px;
    padding-top: 10px;
    box-sizing: border-box;
    background-clip: content-box;
    background-image: radial-gradient(transparent 9px, blue 10px);
}

.box::before {
    margin-left: -20px;
    padding-left: 10px;
}

.box::after {
    margin-right: -20px;
    padding-right: 10px;
}