The box contains a rubber ball suction device attached to a glass column, and four small silicone type rubber bands. You slide one of the rings onto the glass column, then depress the suction device before placing it over a nipple, allowing it to suck the nipple up into the tube before sliding the ring down onto the base of the nipple.
A caveat here: This is very size specific. I would recommend checking this out at your local adult toy store for scale before purchase. The glass column itself is a little narrow. It barely, barely worked on my nipples (which I will admit, are probably a bit larger than average, but not too extreme!). If nipples were quite small (such as on a male) the column would likely be quite a bit bigger than necessary.
This size difference wouldn't be such a big deal if the way the item was intended to work wasn't so dependent on size. The rings are roughly the same size as the glass column, and so being slid down onto very small nipples, I can see where they would simply fall off. For someone who is just the right size, on the other hand, this is an interesting toy.
Once upon a time, we had snakebite kit type nipple suckers which I adored. We also had little nipple "nooses" which we had a lot of fun with - particularly being worn under clothing to maintain permanently erect nipples when out in public. This promised a similar type of sensation to these two, hopefully combining the best of both worlds.
Master had a little bit of struggle with the placement of this, again because the sizing was pretty tight. The suction was pretty delicious; not super-strong so it wasn't painful, but strong enough that you couldn't ignore what was going on. There's a sudden snapping shock of sensation when the band is rolled down and onto the nipples. It definitely made me jump. You'll want to steel yourself for that moment; it's not painful like the bite of a clamp, but somehow extremely jarring. With the band in place, the suction bulb can be gently wriggled off. That's just the start of the fun.
The light binding of the nipple isn't painful, but it does ensure that the nipple will stay hard. This is where I think it would come in handy for people with inverted nipples. The band around the base will allow for plenty of nipple stimulation; it's small, and so doesn't block off the nipple in any way. If desired, you could play with the nipple manually or orally or use other toys such as clamps, vibration, anything you would like to stimulate the nipple while it's standing up proudly. The visual is kind of nice too, as it does stand it up high and hard, the suction making it quite tall.
After a little time, I reminded the Masterly type of the "other" place that we often used the snakebite style suckers in the past. Yep, that sensitive little nub between the legs. I was worried with the narrow glass tube that this wouldn't work well, but when it comes down to it, my clit isn't terribly huge. And it does love the suction. Oh my.
The Masterly one got an evil glint in his eye. He loves playing with toys. And suction things, too. It wasn't more than a minute before he was between my legs. There was some initial yelping and protest as I was still a bit sore from some rough activities the night before, but within a minute or two he had me purring like a kitten and squirming with splayed thighs. He knows just how to push my buttons, this one in particular.
At any rate, before long, he had the toy poised over my clit. The suction here was far, far more intense of a sensation than on the nipples. It still wasn't painful, but that may be just because I enjoy the sensations so much. I'm not sure if the silicone ring ever made it onto my clit, as I quickly got so aroused by the tugging and pulling on the bulb itself that I was close to orgasm. I never had that jumpy OMG moment that I did when it slid onto my nipples so I suspect not. It wasn't long before I was exploding, and Master was using his mouth to remove the rings from my nipples... ahhh bliss.
Overall this is a fun, non-severe toy that will work well for even those with zero pain tolerance. I still think the snake bit suckers are a little better on my clit but the rings make this unique. I'm interested in finding out how the rings perform in keeping nipples at full attention long-term, under clothes, out in public, but that'll have to wait for another occasion. I do think they'll perform well, though.
A warning: Be sure that the nipple is completely encased in the glass tube before sliding the band down onto the base of the nipple. With one try, it was at a bad angle, and the band slid onto the base of my nipple on one side and the middle on the other side (at an angle in other words). This did result in some pretty intense discomfort, though it was quickly remedied.