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Robert

I can't help with ID but just a friendly suggestion: if posting multiple photos, it helps if they are numbered - easier to refer to proper pics...You could go back (edit) and add the numbers above each pic). Hope you don't mind :)

1. Polaskia chende

2. Stetsonia coryne aka Toothpick cactus/ one of my fav cactus because the spines are sooo evil;).

3. Definitely a Gymnocalycium. Have you seen the flower?

4. Mammillaria schiedeana

5. A Rebutia of some sort, check out Rebutia fabrisii. That seems like a good fit.

6. Echinopsis chamaecereus hybrid, there’s all sorts of these hybrids. Most popular would be ‘Ros Quartz’. Have you ever seen the flower?