Eye to eye tails are used to create what tree climbing instructors call a "closed system", resulting in a finished friction hitch with both ends attached to the connector instead of one hanging loose, as with the traditional hitch or single-eye slit tai. The eye-to-eye tail also allows use of several hitches that are easily learned and extremely smooth performing.
By utilizing both ends of the type of split tail, friction is more evenly distributed, resulting in more consistent friction thorough a knot that is less binding, yet grabs quite firmly. The system is enhanced significantly when incorporating a micropulley that fair-leads the hitch for one handed slack tending.
Prusik Cord Ice 8 mm x 30" G-Spliced Eye & Eye