Selling my Kenko Macro Extensions(Nikon), great for aquarium photos

[xernex]

Hey guys I've got a full set of these:

http://www.bhphotovideo.com/bnh/controller/home?O=&sku=375238&Q=&is=REG&A=details'>http://www.bhphotovideo.com/bnh/controller/home?O=&sku=375238&Q=&is=REG&A=details

Asking $100 shipped OBO...seriously throw offers out to me, these things are taking up space in my camera bag.

 

Hope this isn't breaking any forum rules... it doesn't really fit with the general marketplace items since its not aquarium related, but figured here would be the best spot

[smiz]

Im a noob to photography but i have a nikon d3100. Would this lense work for that and how close do these get? I'd like to be able to get nice close ups of my corals but dont need it insanly close.