From memory it's the same gear as in the depo injection but slow release. So if it doesn't suit you take it out and it's out of your system unlike the depo which has to wear off.

I had no periods for just over a year and then all of a sudden irregular very heavy ones. Got it taken out under general anaesthetic due to incorrect placement of it by original dr.

Big pain in the butt!! I'm sticking to the pill from now on.