I have no idea what species they are and I need to know in order to mix the soil for them when I replant them in larger pots. Any help at all will be greatly appreciated. I have already gone through several identification websites, but so far no luck. Thanks in advance.
After doing more searching, is the one on the left Parodia aureispina? And is the one on the right Mammillaria prolifera?
No, the left one is another Mammillaria. Could it be M. pringlei? The other one is probably Mammillaria vetula gracilis. (It is difficult to see because the light source is behind the objects, and to make things worse I don't collect Mammillaria, just a lot of other cacti.) Sorry for the late answer, I have been away from the forums here for some time.