@media all and (min-width: 640px) and (max-width: 734px){
* {
background: red;
}
}
<div class="row">
<div class="col-12 col-lg-6">
<div class="item"></div>
</div>
<div class="col-12 col-lg-6">
<div class="item"></div>
</div>
<div class="col-12 col-lg-6">
<div class="item"></div>
</div>
<div class="col-12 col-lg-6">
<div class="item"></div>
</div>
<div class="col-12 col-lg-6">
<div class="item"></div>
</div>
<div class="col-12 col-lg-6">
<div class="item"></div>
</div>
</div>