Yes, Mammillaria. Looks like M. lloydii although it should have three spines, not just two. Other similar species are M. magnimamma (very variable but usually has at least one very long spine and less edgy tubercles) and M. roseoalba (usually has more spines).

So ... how about M. sartorii? I think I can see some tiny radial spines on some tubercles.

I will stay with M.lloydi, but what about the dense wool??
Alfonso