HTML

<a href="#" title="" class="btn btn-primary btn-lg box-shadow--2dp">Button 2dp</a>
<a href="#" title="" class="btn btn-success btn-lg box-shadow--4dp">Button 4dp</a>
<a href="#" title="" class="btn btn-warning btn-lg box-shadow--8dp">Button 8dp</a>
<a href="#" title="" class="btn btn-danger btn-lg box-shadow--16dp">Button 16dp</a>

CSS

.box-shadow--2dp {
    box-shadow: 0 2px 2px 0 rgba(0, 0, 0, .14), 0 3px 1px -2px rgba(0, 0, 0, .2), 0 1px 5px 0 rgba(0, 0, 0, .12)
}
.box-shadow--3dp {
    box-shadow: 0 3px 4px 0 rgba(0, 0, 0, .14), 0 3px 3px -2px rgba(0, 0, 0, .2), 0 1px 8px 0 rgba(0, 0, 0, .12)
}
.box-shadow--4dp {
    box-shadow: 0 4px 5px 0 rgba(0, 0, 0, .14), 0 1px 10px 0 rgba(0, 0, 0, .12), 0 2px 4px -1px rgba(0, 0, 0, .2)
}
.box-shadow--6dp {
    box-shadow: 0 6px 10px 0 rgba(0, 0, 0, .14), 0 1px 18px 0 rgba(0, 0, 0, .12), 0 3px 5px -1px rgba(0, 0, 0, .2)
}
.box-shadow--8dp {
    box-shadow: 0 8px 10px 1px rgba(0, 0, 0, .14), 0 3px 14px 2px rgba(0, 0, 0, .12), 0 5px 5px -3px rgba(0, 0, 0, .2)
}
.box-shadow--16dp {
    box-shadow: 0 16px 24px 2px rgba(0, 0, 0, .14), 0 6px 30px 5px rgba(0, 0, 0, .12), 0 8px 10px -5px rgba(0, 0, 0, .2)
}