3-stars means "It's Okay". And that was our mutual consensus. We ordered these as an add on, figuring the risk was worth it for the price. 2 loupes for $5.  My husband uses loupes frequently in his work and hobbies, and already owns a 10x and 20x loupe.

Pros:
 * metal casing,
 * glass lenses
 * 21 mm lens (good size, not too big or too small for portability. this is the size my husband prefers)
 * great for hobby use (from coins to stamps to biology), classroom use, etc.
 * clear magnification; no distortion when used correctly

Cons:
 * not necessarily a 30x.  The loupes we recieved were approximately 15x, when tested against our (much more expensive) 10 and 20x loupes.
 * 30 x 21 mm only ink-stamped. it will eventually wear off.
 * one glass housing seemed a bit loose

Something we noticed, which I did not see in any other review: The label on the box (each loupe is individually boxed) includes this warning: "Picture and Description are for illustration purposes only. Actual product may vary."
Based on that, and on the many reviews here, I think it is quite likely that some people have in fact received 30x magnification, while many others have received something of a different power.

It is a good little loupe, and the price is great. You just need to be aware that you may or may not get a 30x power if you order this particular item.