Pros: easy to carry, small, comfortable, reusable, long-lasting, cheap, less painful periods, no leaks, no smell,
Cons: takes a little learning but not much
I bought this back in the last 90s. It changed my life. My periods became shorter and less painful (and no nausea, dizziness, fevers, etc. like were normal -and still are- if I use regular tampons or pads)... basically, for the first time in my life I had a period where I *might* pop a couple ibuprofen for a harder day of cramps and that's it. It was wonderful.
It does take a little learning at first to put it in right, but luckily you can practice that when not on your period, unlike tampons. Once learned, it's easy-peasy and you can do it half-awake or dead-drunk lol.
It also lasts so long between emptying that it can be scheduled to do in private at home on most people's schedules.
I could always, always feel tampons, no matter what brand or how placed... but when in right I couldn't feel The Keeper. I never had a leak that wasn't caused by my own fault of forgetting to empty it on time.. and that was 2-3 times in 10 years, despite a very active lifestyle.
Just a few months ago I retired my Keeper and purchased a DivaCup just to try out a different style of cup, not because I didn't love my Keeper. After 9 years it was showing that it was finally getting old... still usable, but getting about time to get a new one.