Box One Chain Tensioners

Box One Chain Tensioners formally called the Limit
Box One Chain Tensioners 3/8″. Holds your wheel back and centered. Prevents slipage if you have slipping occuring. You can also use large frame washers which provide more grip than an a standard axle bolt can. Chain tensioners are however a hassle when it comes to removing your wheel for a tube replacment.
This was called the Box Limit Chain Tensioner. This fits most 10mm axles.