This stiff tether has split legs, allowing you to use your Singing Tree Rope Wrench with a DMM Hitch Climber pulley.  

The benefit is your system then sits symmetrically without putting a twist off to one side normally normally caused by a standard stiff tether.

Some have also applied this to the Zigzag, though Petzl do not endorse the use of the Zigzag with a Wrench in SRT.

The Standard 30cm suits longer hitches like the VT, while the Short 25cm suits a short hitch or..... Zigzag.

Made from Donaghys Armor Prus and machine sewn by the Gravity Lab.