These stick on “blockers” don’t work. I am EHS and can tell you with certainty (because I feel the fields) that they are not blocking anything. You must use substantial materials like those used in faraday cages (silver and copper), which are now manufactured in materials and fabrics, or avoid EMF use period. Just look at military use for example. They are not using stick on blockers. Follow Ty’s advice for minimizing and avoiding EMF, and look up EMF blocking fabrics, building materials, etc… for the real blockers.
Of course, scientific seesawing like that doesn’t provide a lot of clarity or confidence for the 90 percent of American adults and roughly 80 percent of teens who report having a cell phone. So how concerned should you be about cell-phone radiation? Consumer Reports’ health and safety experts conducted a thorough review of the research and offer some guidance.

In March, however, a peer-review panel of 11 experts from industry and academia voted to advise the agency that it should raise the confidence level from “equivocal evidence” to “some evidence” of a link between cellphone radiation and brain tumors in male rats. (The female rats did not show evidence of a link between the radiation and such tumors.) Two panel members, Lydia Andrews-Jones of Allergan and Susan Felter of Procter & Gamble, proposed the risk upgrade.
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.
First, you must have a proper meter. To check for magnetic field emissions, an AC Gaussmeter will work. Most AC gaussmeters will have an internal probe. Simply position the gaussmeter on the phone. Note carefully where the meter is positioned. Make a call and watch the readings. Notice the highest and lowest readings, and make a mental note of the "average" reading. Now, insert the magnetic shield, and repeat.
A 2010 review stated that "The balance of experimental evidence does not support an effect of 'non-thermal' radiofrequency fields" on the permeability of the blood-brain barrier, but noted that research on low frequency effects and effects in humans was sparse.[4] A 2012 study of low-frequency radiation on humans found "no evidence for acute effects of short-term mobile phone radiation on cerebral blood flow".[5][6]
What are the health effects of mobile phones and wireless radiation? While Australia has led the world in safety standards, including compulsory seat-belt legislation, plain packaging on cigarettes, and product and food disclosure legislation, it falls behind in addressing the significant issues associated with mobile phone use. In this Dean’s Lecture, epidemiologist and electromagnetic radiation expert, Dr Devra Davis, will outline the evolution of the mobile phone and smartphone, and provide a background to the current 19 year old radiation safety standards (SAR), policy developments and international legislation. New global studies on the health consequences of mobile/wireless radiation will be presented, including children’s exposure and risks.

I received mine yesterday in the mail. I have a Samsung Galaxy Note 3, and I cannot use this sock unless I take the case off. This is one thing I did not know when I was purchasing this material. I am trying it out as stated, however even when I use a rubber case or a very thin case with the sock its very tight to get off. I think the manufacturer needs to allow more room in these and or not state that it fits the larger phones at 6 inch. They should state that without the case it will fit. I am in the first day of walking around without a case, and just the sleeve. Its different, and if I drop my phone I'm in a world of hurt. I like the idea of this, but I was also surprised when the material really only feels like felt. It's not like the RF fabric that I have seen, and hopefully this is some kind of special blocking material as stated. I do like the idea, and I agree that cell phone radiation exist. Ill come back and give five stars if I really notice a difference, however if I drop my phone because I dont have a case I'm going to be posting less stars.

Use a corded home phone whenever possible, to minimize the need for a cell phone. Cordless home phones emit RF, so replace cordless phones with corded home phones. One initial step is to unplug the electrical cord of the cordless phone base station when the phone is not in use, because otherwise that base station will emit RF nonstop. Note: you can plug a corded phone handset or corded headset into your VoIP connection.  
A third requirement was for the FDA to create a formal interagency working group to oversee the work and provide input. The purpose of this was to alleviate any perception that the industry was paying for a result, not for the research itself. But the fourth and last requirement was considered by Dr. Carlo to be highly critical: “Everything needed to be done in sunlight. The media had to have access to everything we did.”
When you need to get further from your headset, this extension does the trick. Three feet long, white, and very light weight. Has standard iPhone 3.5 mm, 3 band plug and socket. Simply plug one end into your iPhone, and plug your headset into the other end. You can daisy chain up to 4 extensions to get a total length of 12 feet if you need it! Available in black or white.
Still think Pong’s SAR testing prove you are safer? Take this for example, the Samsung Galaxy Note 5 SM-920V FCC ID A3LSMN920V (Official FCC Doc) made for Verizon has an FCC measured SAR of only 0.21 W/kg (watts per kilogram) and the Apple iPhone 6 Plus exposes a user’s head to a whopping 1.18 W/kg FCC ID: BCG – E2817 Apple iPhone 6 SAR  (Official Doc Page 138).  That’s a dramatic difference of several hundred percent from highest SAR to lowest SAR on these high-end smartphone devices.

We used a few measuring devices to test and see if this product actually blocks radiation and RFID, including a very sophisticated EMF reader. I am glad to say that this is actually a very effective way to reduce radiation. It is most effective on the front side, and when you have it closed and latched, there is very little exposure - only along the top, side and bottom opening.
Radiation is all around us. Power lines, appliances, and electronic devices all emit electromagnetic frequencies. One source that many of us keep close, perhaps too close, are cell phones, tablets, and other mobile devices. They all use radio frequency (RF) electromagnetic energy, a form of non-ionizing radiation, to communicate. Research has shown that this type of radiation is not benign or harmless to the human body, especially children. Exposure to cell phone and Wifi radiation has been linked to fatigue, dizziness, mental fog, and even worse. As a result, the demand for products that reduce exposure to device radiation is on the rise. In fact, "How can I protect myself from cell phone radiation? What do you recommend?" is a question we get all the time. So, to help, I wanted to offer my thoughts on five products I've found that I believe are worth a look if you're interested in reducing your exposure to cell phone and mobile device radiation.

We used a few measuring devices to test and see if this product actually blocks radiation and RFID, including a very sophisticated EMF reader. I am glad to say that this is actually a very effective way to reduce radiation. It is most effective on the front side, and when you have it closed and latched, there is very little exposure - only along the top, side and bottom opening.
According to the FTC, there is no scientific proof that so-called shields significantly reduce exposure from electromagnetic emissions. Products that block only the earpiece – or another small portion of the phone – are totally ineffective because the entire phone emits electromagnetic waves. Such shields "may interfere with the phone's signal, cause it to draw even more power to communicate with the base station, and possibly emit more radiation."[47] The FTC has enforced false advertising claims against companies that sell such products.[48]
None of the three cases contain metallic parts, which are known to affect SAR, but all increased the user’s radiation exposure. The effect on radiation exposure would likely vary with each of the hundreds of cases on the market, and each would have to be tested individually to come up with an exact measure. The results in Table 1, however, are believed to reflect the range of radiation increases.
Initially leaked in 2016, results from that $25-million study provided the most compelling evidence yet that RF energy may be linked to cancer in lab rodents. The strongest finding connected RF with heart schwannomas in male rats, but the researchers also reported elevated rates of lymphoma as well as cancers affecting the prostate, skin, lung, liver and brain in the exposed animals. Rates for those cancers increased as the doses got higher but the evidence linking them with cell phone radiation specifically was weak by comparison, and the researchers could not rule out that they might have increased for reasons other than RF exposure. Paradoxically, the radiation-treated animals also lived longer than the nonexposed controls. The study results were reviewed by a panel of outside experts during a three-day meeting that ended on March 28. They concluded there was "clear evidence" linking RF radiation with heart schwannomas and "some evidence" linking it to gliomas of the brain. It is now up to the NTP to either accept or reject the reviewer's conclusions. A final report is expected within several months.
Radiofrequency radiation is a form of electromagnetic radiation. Electromagnetic radiation can be categorized into two types: ionizing (e.g., x-rays, radon, and cosmic rays) and non-ionizing (e.g., radiofrequency and extremely low frequency, or power frequency). Electromagnetic radiation is defined according to its wavelength and frequency, which is the number of cycles of a wave that pass a reference point per second. Electromagnetic frequencies are described in units called hertz (Hz).