Anyone ever use this. It's a lansinoh latch assist, typically for those with flat or inverted nipples.

is it like a suction cup to make nipple hard?

Kinda. I've been leaving it on two hours a night in hopes of drawing out my nipple out more permanently because my nipples are pretty damn flat and I want to breastfeed longer than three months like I did with my daughter. The whole experience with her was horrible.