Actually works
I've tried many different running "endurance enhancers", and OPTMLs Running Performance supplement has been by far the best.  It definitely  increases my endurance for long distant running, and holds it's endurance boost afterward for extra cross-fit workouts.  I am very impressed with this products ability to keep me going throughout my runs, mile after mile.  Definitely recommended and a great bang-for-your-buck.
Rating: 5 stars