If you are finding it tricky to open the pottles, here are some tips;
Use scissors to snip the perforated edge of the lid
A rounded teaspoon end can be used as a handy lever to prise the lid off
Sometimes the lid is stuck on by suction when it is in contact with the yoghurt. We worked out that snipping the opening then turning the opening AWAY from you ( and maybe on the edge of the sink the first time!) and then gently squeezing the pot makes the lid pop open very easily.That trick also works even if suction isn't an issue.