These are for a small amount of cremains. My family has a few of these, to have a small amount of the deceased. The main urn is significantly larger and is with the widow.
My mom and aunts split my grandmother's ashes evenly in 3 identical urns. We also used incredibly tiny amounts in urn jewelry (jewelry with a small chamber).
My 2 sisters and I each have one of these small urns of our grandmother's ashes. Our mother has the large urn. Doesn't necessarily make it common, just volunteering that I have one.