This is a guide to familiarize buyers on the difference between normal depth keys, and bump keys.

Normal depth keys can be used for determining the key code of a lock. This is done with the lock disassembled so that the lock pins can be seen. Normal depth keys are cut from most shallow to deepest depth. In other words, from 0 to 9 depending on the brand of lock the key fits.

Bump keys are designed for one purpose. To open a lock that someone has no key for. Locksmiths have used this method of opening locks for a long time, but, it has just been discovered by some enterprising people who are capitalizing on that discovery by demonstrating how to use them on social networking sites and selling them here on Ebay. Bump keys can, and in some cases, are, used to gain entry for other than legal purposes. I think you should know the difference between the two.
Depth keys are a tool used for purposes of commerce, like locksmithing. Bump keys, in the wrong hands, can be used for illegal purposes. I hope that this helps distinguish between the "actual" depth keys, and the bump keys that are being sold here on Ebay.