|Drop falling from an icicle, shot using a 7mm extension tube|
Dripping Icicle on Flickr by Archaeofrog
There are two main types of extension tubes: those that maintain the electrical connections with your camera body and those that do not. Both types of extension tubes are available on Amazon. I used the generic Fotodiox set of three tubes pictured below for all shots in the article.
Click here or on the image above to search for extension tubes.