This pack was my first period underwear purchase a few months ago and I was so worried about leakage that I went for the heavy option. Turns out I didn't need to worry as this product works 100%.
I am a new convert, no need for pads any more, these are amazing!
The only time they have leaked was when I took my cup out at night and didn't put it back in during a very heavy flow, and didn't change the pants either - they just got overloaded from basically 24 hours of flow, and actually it was the smallest little leak so I was really happy - didn't affect my clothes or the sheets.
These are so great on light-moderate days by themselves and with a cup on the heavy days.
I know that the patented technology has to be made from plastic, however I really wish I could feel amazing about this product knowing that it was 100% petroleum-based plastic free, hence why I've rated it 4 instead of 5. One day...
In the meantime I will probably order my next set for light days from She Thinx, just because they offer an organic cotton option that has less plastic in it.