These large sponges are most suitable for women with heavier flows or women with a degree of vaginal prolapse.
They are used like tampons, and can't be felt at all when they are worn. When they are ready to change you feel a slightly heavy sensation - just change one for the other and rinse in water then leave it to air dry.
If you want you can tie some dental floss around them to aid removal but to be honest they can't 'get lost' as they gradually move downwards as they absorb the menstrual blood.
Each pair will last about 6 months.