These nifty chain tensionsers from Surly serve two very important needs...keeping your wheel tight and free from chain stay rub and opening beer bottles.  One works well but, a pair will keep your bike and soul in perfect symmetry.

BTW....if you have a SURLY Steamroller......these are one of the few chain tensioners that will fit your breeze style dropouts, fool!

Fits: 3/8" Axle
Color: Silver
Intended Use: Single Speed
Invoice Description: SURLY Tuggnut tensioner for horizontal dropouts
Country of Origin: TW