First some specifications on the product, before expanding to the rest of the review: this is a Kegel exerciser comprised of two parts. The first is an egg trainer and a double egg trainer.
Then there are the slings that are used to hold said trainers.

The eggs are to be inserted into the slings and then placed into the vagina. The slings allow easy removal of the balls.

As for who the product is for, well, there should be little doubt that it’s specifically for women. Given the size of the balls and lack of a base it is only for vaginal muscle strengthening. If this managed to fit within the anus, it could be sucked in and with a base, it might not bestopped. As this is a tool to strengthen Pubococcygeal (PC) muscles, it cannot be explained without explaining why kegels are important.
Kegels.

The purpose and benefits of kegels vary by gender, but the goal is the same, increased blood flow to the sex organs. For men this may mean stronger orgasms, stronger erections and better control of the sex muscles and urinary tract. Clearly improved erections are impossible for women, but there are numerous other benefits.

Improved orgasms.

Better control of urinary tract.

Improved delivery during childbirth and helps to tighten the vaginal walls after childbirth.

Like all exercise, the actual benefits depend upon the effort given to the training and how well the training, described later, is followed.

Another possible use for the eggs is internal stimulation. It could be inserted by a partner or the user and either used with the internal muscles or the strap. This shows not only how it could be used for non-Kegel related activities, but also partner play.

The eggs and harness are both smooth to the touch and flexible. The flexibility is for maneuvering them during practice. It lacks any sort of texture for the purpose of stimulation, but there’s a good reason for that. Another benefit is that it lacks any unpleasant smells or tastes.

The design is made for simplicity and beginners. There are three balls of different weights and two different slings. One sling holds one ball and the other holds two. This design is allows for a gradual increase in weight to train with the weight that feels right.

The eggs themselves are pretty basic. As explained previously, they're smooth and look like Easter eggs. When shaken, the weight rolls around inside, bumping against the wall of the egg.

As for travel, that depends on how they're packed. If left inside the sling it may seen as clearly a sex toy, or a very odd slingshot. If packed separately however, it's less obvious what the purpose is for each component. It is worth noting though that the eggs make a lot of noise when shaken, so it's best to keep them packed in something just to be safe.

Part of the performance is dependent upon the ease by which objects enter the vagina. Those with smaller vaginal openings may have issues with these balls. It will take a moderate amount of lubricant and time to insert the balls and even then they may not insert easily.

Once inserted, they will feel like peculiar. According to my girlfriend, they will feel weird, almost like trying to poop out of the vagina. While inserted, any shift or movement may also move the balls, which also feels weird.

After insertion, they should be kept inside for one hour each day for a week. After said week, move onto the medium sized ball, then the heaviest ball for week three. Week four involves switching to the two ball sling and the two lightest balls, then the light and heavy ball for week five, and finally the heaviest two balls for week six.

The actual results will depend upon how much effort is devoted to the exercises. It’s the beginning of the regimen for my girlfriend, so wait for the follow-up to find out how it went. In the meantime, read up on kegels to learn more.

There are two materials to be considered, the plastic the eggs are made of and the silicone of the harnesses. For either material care is pretty simple. As both materials are nonporous, it is easily sterilized with a quick soak in hot soapy water. Other methods include, boiling, using the dishwasher, (not my first choice admittedly) or isopropyl alcohol.

As for care, the most important thing to remember is that silicone cannot touch other silicone or it risks melting. When storing the slings, keep them enclosed in a sealed container of some sort, anything as complex as a container or simple as a box or a sock would work. Just prevent it from touching other silicone toys.