6 Pcs Mini 30X 21mm Singlet Jeweler's Jewelry Loupe Magnifier Magnifying Glass Silver w/ Box

Second Update: these seem to have a focal distance of roughly an inch. The power of a simple hand magnifier, I believe, is based on taking a lens with a focal length of ten inches and calling that 1x. A lens of a focal length of five inches would be two x or two power. A lens with a gocal length of two inches would be five power or five x. I have a five power lens which, indeed, does focus at roughly two inches.In other lens parlance, a lens with a focal length of one meter, which is a thousand millimeters, is called a one diopter lengs. A two diopter lens is one of focal length of half a meter or five hundred millimeters and so on. Therefore, if a lens had a focal length of roughly thirty three millimeters, which is just a bit over and inch which is 25.4 millimeters, that lens would be thirty diopters. These loupes, therefore, probably are close to thirty diopters but in linear measurement, which is how they should be rated, they are roughly ten power or slightly less. Since, as I may have stated below, ten power is a pretty standard, if not the most common standard, for this type of magnifier, it is a good guess that this is roughly ten power. Things still get unclear, though, since, in my collection of loupes, I actually had a five power and a seven and a half power loupe. If all this is as clear as mud, just remember that these are excellent buys. They are especially good buys if they are triplet lenses but, as of yet, I do not have the ambition, with my eyesight, to unscrew the retaining ring to remove the lense. Real hastings triplets and even achromatic doublets, can or used to be rather pricey lenses. Back when my sister took a botany course in the seventies, she was required to purchase a ten dollar, ten power, loupe which, despite working well, was actually two simple lenses with an air spacer in between.UPDATE: I believe that, purely by convention, that the power of simple magnifiers is that they are normally based on typical reading distance which is, by convention, is taken as ten inches. If that is the case then these lenses, which seem to focus around an inch, should be about ten power in linear magnification. Just by crude estimate, they do seem to be from five to ten power which is a useful loupe. By this reasoning, if, by convention, you took the standard screen or reading view distance as rought a foot, then that would be roughly thirty centimeters, and they could be labeled, as a wild quess, as thirty x. Just look through one and, if you do need more power, go to a more epensive loupe or even a stereo microscope. Everything below still holds including whether they are actually rather expensive triplets as they claim. They may be a mislabeled product that cannot be sold without getting a lot or returns from irate scientists or jewelers. They are great, though.If I drag out my loupe collection, I may update this once again and subject you to my lousy math.These thing are mislabeled as to the power. They are marked as 30x21mm which, in standard terminology should mean that they are thirty power and twenty one mm in diameter.They are more like ten power or possibly less but they really magnigy and show a clear crisp image.The way you use a loupe is to hold it up to your eye and bring what you are trying to view up to the loupe. Do not try the Sherlock Holmes routine of holding the magnifier over the object. This is most people the idea that you use a magnifier this way but it is only good with large diameter glasses for print.My paternal grandfather was an entymologist who worked for the Agriculture Department of the State of Alabama in Cullman County, Alabama north of Birmingham. When I was eight back in nineteen fifty four, he gave me two well used but very fine loupes, both Hasting's triplets. One was a standard ten power and the other, slightly smaller, was fourteen. These seem to be standard powers or used to be.I have, over the years, acquired a collection of loupes. I have a five power, ten, fourteen, twenty, and even a real thirty power which is small and rather hard to use since it focuses so close to the object.The mose expensive loupes are Hasing's triplets which are three lenses of different types of glass cemented together. This gives a highly corrected, color fringe free image. After this comes a two lens achromat, either cemented or air spaced. Then you can get two simple lenses with an air space between them. You could evern get a simple but powerful simle lens.All the above would work reasonably well especially if made of glass and not plastic. I have my late sisters botany required ten dollar loupe from the seventies and it is two lenses with an air space. It is ten power and she got it with her textbook from the University of Maryland bookstore. It works perfectly well.This loupe is marked as a triplet but I have no real desire to unscrew it to see if it is or not. At two dollars and thirty cents a loupe I could care less but, if they are not triplets then they are marked wrong a second time which might pose legal problems and may explain why the things are so cheap to begin with.The lenses do seem to be glass. The way to test this easily if you take the lens out is to hear a paper clip wire red hot and touch the edge of the lens. Any kind of plastic will melt. They do look like glass though so why bother.Would I buy them again. I actually have bought a toral of twenty four on two more separate orders. They make the dandiest little gifts and stocking stuffers you can imagine and I plan to get good use of my supply. I already gave away two to the couple my wife and I dine with on a regular basis and they were totally impressed. Most people have never even seen a loupe so they are wowed by them.Once again, my guess is that they are ten power or perhaps five power. It also now occurs to me that one of my old loupes is seven and a half power.In closing: magnification for lenses, binoculars, telescopes, microscopes, etc., is, by convention, linear. That is, a two powe glass mage a five inch line look ten inches. A two by two square as opposed to a one by one square would actually have a four power area magnification but this is not how magnification is calculated except, it seems, in some parts of Asia where any bigger number is desiarable. I have seen ultra cheap cinoculars advertised on TV as a hundred x which means they are actually ten x or power. Buyer beward.

These are NOT a "30X Jeweler's Loupe" set, but they are a reasonably sturdy, inexpensive (I paid $12.15 for 6) set of magnifiers that should stand up to moderately heavy use. To estimate the "power," for me an in-focus image of an object 7mm long fills the 21mm diameter lens, so simple math says that's 3X magnification. At just over 2 bucks each, these are inexpensive enough that I could put one every place in my house that I thought I might need a 3X magnifier and still have some left over to use as holiday stocking stuffers. (Just tell anyone you give them to that it's really a 3X magnifier, not a 30X loupe as the labeling incorrectly claims.)

Excellent price for this bundle! The loops work well, but have a VERY narrow viewing window... Hard to use.

The tiny screws holding the two parts together area falling out, and I have used these only for a month. Three students on my first plant walk returned their lenses with the lens separated from the swing cover. Was very excited about the great price, but not if they cannot be used properly.

These are exactly what I needed for a science class that needs close-up magnification. At an inexpensive price, I was able to purchase one for each student to keep.

I ordered these loupes for some schooling I am doing. I was excited for a cheap 30x loupe because I am using a 10x one now. These had no different magnification than my 10x loupe. They are incorrectly marked and I wasted my money. I since have a verified 20x loupe and the difference is noticeable. I will not be buying these again.

It works well, as expected. I really only needed one so I don't know why I bought six. If the one I'm using breaks, I guess I'll be glad I have another if I can remember where I stored them. But, so far #1 is holding up well.

Great value for the price! I use and lose loupes constantly. Order these!