This small magnifier has an amazingly powerful 5X power, and the lens measures 28 mm in diameter (just over an inch across). The lens is both clear and lightweight, and will fit right onto any keychain. Aside from the obvious (in helping you see tiny keyholes), this ultra-portable magnifier is also great for examining coins, stamps, or any other object with small print.
These little magnifiers come in assorted colors - so go ahead, grab a few for yourself and a couple friends!
More information: http://www.braillebookstore.com/Keychain-Magnifier.1