It’s easy to call any case a product designed to block smartphone radiation.  What you need to look for is credible, quantifiable claims that highlight a case’s ability to reduce your exposure to the harmful radiation. Look for relevant  certifications from credible organizations (such as FCC accredited laboratories) that will vouch for product claims, and read product reviews online.

A phone's specific absorption rate (SAR) reveals the maximum amount of radiation the human body absorbs from the phone while it's transmitting. SAR testing ensures that the devices sold in the U.S. comply with the Federal Communications Commission (FCC) SAR exposure limit, but the single, worst-case value obtained from this SAR testing is not necessarily representative of the absorption during actual use, and therefore it is not recommended for comparisons among phones. In short, selecting a lower SAR phone will not reliably ensure lower radiation absorption during use. The FCC has more information at Specific Absorption Rate (SAR) For Cell Phones: What It Means For You.

An analysis of an "eagerly anticipated" study using rats and mice by the National Toxicology Program indicates that due such issues as the inconsistent appearances of "signals for harm" within and across species and the increased chances of false positives due to the multiplicity of tests, the positive results seen are more likely due to random chance. The full results of the study were released in February 2018.[10]

One of the most robust animal studies in the world comes from the US government. In 1999, during the Clinton administration, the Food and Drug Administration asked the National Toxicology Program (NTP) to study the toxicity and cancer-causing capability of cellphone radio-frequency radiation. At the time, health officials felt epidemiological studies in humans wouldn’t answer these questions, so the NTP embarked on studies in rats and mice.
Thus far, the data from studies in children with cancer do not support this theory. The first published analysis came from a large case–control study called CEFALO, which was conducted in Denmark, Sweden, Norway, and Switzerland. The study included children who were diagnosed with brain tumors between 2004 and 2008, when their ages ranged from 7 to 19 years. Researchers did not find an association between cell phone use and brain tumor risk either by time since initiation of use, amount of use, or by the location of the tumor (21).
Since use of mobile phones by children began at a later stage compared to use by adults, the effects of exposure to mobile phones in this population have not yet been investigated. Considering their health sensitivity, the long life expectancy in the young population (probably involving the accumulation of significant exposure and development of morbidity in the long-run), and ethical issues involved in decision making regarding the population of minors, additional precaution is required in this population. Therefore, the Ministry of Health advises parents to reduce children’s exposure to mobile phones as much as possible, consider the age they start using them, reduce the amount of time mobile phones are used, and in any event, make sure they use earphones (not wireless) or a speaker when using the mobile phone.
This is a 2 pieces of plastic sandwiched together by glue. Don't believe me? Take it apart. This item works no better than the existing case on your phone. If you are that concerned with cellphone radiation, you should be equally concerned about the cheap plastic and toxic glue that this is comprised of. Also know the fact that they've stolen $25 from your wallet when you purchase this hokey product...Technology at it's finest.

“Epidemiological studies are targets for fixing the outcome because they’re observational in nature instead of experimental,” Dr. Carlo explains. “It’s possible to design studies with pre-determined outcomesthat still fall within the range of acceptable science. Thus, even highly flawed epidemiological studies can be published in peer-reviewed journals because they’re judged against a pragmatic set of standards that assume the highest integrity among the investigators.”

The government, however, does not require phone manufacturers to consider the effect of cases when they conduct compliance tests to meet the FCC’s allowable radiation exposure limits. The significance of this omission was underscored by tests commissioned by case-maker Pong Research and submitted to the FCC in May 2012. Those tests showed that three models of cases made by competing companies and used with an iPhone4 increased the phones’ Specific Absorption Rate, or SAR – the amount of radiation absorbed by the user’s body – by 20-to-70 percent (Table 1).
I love these radiation protection cases. It's a great size for my iphone, and I can even talk on the phone with the phone inside the pouch - perfect sound quality. The only thing I would recommend is that a snap be added to the opening -- it is slippery material. You can tell the company took care in producing a quality product -- it is constructed very well. I recommend this product to cell phone users! Oh, I also got this so quickly!! It arrived within 2-3 days of ordering, and it comes from the UK!! Amazing service!!
Epidemiology studies investigating cell phone use patterns with human cancer risk have produced inconsistent results. Some studies enrolled people who already had tumors with suspected links to RF radiation, such as gliomas, acoustic neuromas and salivary gland tumors. Researchers compared the self-reported cell phone use habits of the cancer patients with those of other people who did not have the same diseases. Other studies enrolled people while they were still healthy, and then followed them over time to see if new cancer diagnoses tracked with how they used cell phones. All the epidemiology studies, however, have troubling limitations, including that enrolled subjects often do not report their cell phone use habits accurately on questionnaires.
At high power levels, RF waves can heat up water molecules (which is how microwave ovens work). Scientists used to focus their concerns on the possibility that such heating of human tissue, which is mostly water, might damage cells. In fact, the FCC’s test of cell-phone emissions—which was set in 1996 and which all phones must pass before being allowed on the market—is based on that effect.
Searching PubMed for studies published in the past 10 years, we found 102 studies that ultimately resulted in 12 relevant systematic reviews. To limit bias in our assessment of the literature, we used a validated critical appraisal tool called AMSTAR to determine the quality of each review. Eight of the reviews were critically low quality, two were low quality, and two were moderate quality.

Let’s say you are in class, or at the movies, and you don’t want your phone to ring. Slip it into the fully shielded slot. In this position, RF signals in or out will be reduced almost to zero, which is enough to stop the phone from ringing in most circumstances unless you have an especially good connection. You can also store chipped cards (like credit cards) in here to prevent unintentional reading.
Because of inconsistent findings from epidemiologic studies in humans and the lack of clear data from previous experimental studies in animals, in 1999 the Food and Drug Administration nominated radiofrequency radiation exposure associated with cell phone exposures for study in animal models by the U.S. National Toxicology Program (NTP), an interagency program that coordinates toxicology research and testing across the U.S. Department of Health and Human Services and is headquartered at the National Institute of Environmental Health Sciences, part of NIH.
One of the studies reports that male rats exposed to very high levels of radiofrequency radiation grew tumors around their hearts. Female rats exposed to the radiation didn’t, and neither male nor female mice showed obvious health problems in a second study. Neither study turned up clear evidence that radiofrequency radiation causes brain tumors, although the researchers are continuing to investigate. The studies are drafts that haven’t yet been reviewed by outside scientists.
An analysis of data from all 13 countries participating in the Interphone study reported a statistically significant association between intracranial distribution of tumors within the brain and self-reported location of the phone (7). However, the authors of this study noted that it is not possible to draw firm conclusions about cause and effect based on their findings.