I don't know if they would be suitable for someone with an extra long vagina, sorry. The general advice is that if you can use a tampon, you can use a cup, so maybe that's not the case for you.
However you can sleep in them. When you insert it you fold it once, then twice. When it is inside you twist and it springs open forming a seal below the cervix. So you could do gymnastics and nothing would seep through. They are very comfortable to sleep in, you can't feel them at all.
If you are going to be in public during your period, you can take a bottle of water with you for rinsing between uses. However it really is ok to reinsert without rinsing for one or two uses, there is no infection risk as long as you wash your hands before as well as after.
There are a few different brands. I use a mooncup, there is also a ladycup, lunette, keeper menstrual cup and diva cup. There may be more too. They vary in the amount they will hold, so my advice would be to read their websites and make a decision based on how heavy your flow is. I got mine in a chemist in Britain, I'm not sure where they are available here other than online but the website of your chosen cup should give you the details of how to purchase and any local stockists.
Well, my overnight run went great. No leaks, and I woke feeling clean, not messy which was great I'm seriously amazed at how comfortable it is!
Still trying to get the hang of this removal thing. Very glad I don't have to remove it very often.
RE: being in public... I think the best part is because that you can leave it in for up to 12 hours, there's not a real huge risk of having to sterilise it. Just give it a wipe if you have no access to water, and reinsert
Someone did a little comparision of a few different ones. Let me try to find it ... Ok... google menstrual cup comparison. And click on the first one, it says "About Cup - Reusable Menstrual Products".
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