[edit, March 23, 2014]
The many five-star reviews of this terrible loupe call into question the perception of the average person, even the average loupe buying person. This has distorted optics, making it very hard to use. The magnification is about 7x or 8x, and MOST DEFINITELY IS NOT 30X! Someone should report this to Amazon, because this is simply a lie. It even says 30x on the product itself, but set it side by side with a high-quality 10x loupe, and you'll see that it isn't even as powerful as 10x. You'll also see that a high-quality product is so easy to use, but this is a LOW QUALITY product, making it very, very hard to use it well. My original review says the rest; I haven't changed my position except to find it very weird that such a little piece of junk can get as many 5 star ratings as one that is of the highest quality. That doesn't even make sense. Do they pay people to write these reviews or something?
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Original review follows:

There are many aspects of a loupe which you can rate or compare. The size, weight, construction, materials, and most importantly the magnification, clarity and non-distortion. This loupe basically fails on many accounts.

Pro: the lens is glass, the rest is stainless steel. It's compact and has a nice weight in the hand.

Con: The viewable glass is  inch in diameter. That's a small loupe. The image is warped and wavy. The magnification is not even 10x, much less 30x.

Amazon sells several very fine loupes. It's hard to see through the comments, so I bought 9 different loupes from Amazon recently, some quite expensive, and compared them. This was the worst of the ones I bought. There are probably others worse than this, but I didn't get every kind. I avoided the all-plastic construction and went for glass and metal. Anyway, you can do better than this, and it's definitely worth spending a little more money to get one with a clear, non-wavy image. (by the way, Loupes are not meant to be held high above the subject matter. Hold them down fairly low for the least distortion.)