How long does this leash get when fully stretched? How does the sizing work for this product?

Our leashes are all 6 feet long. This is the standard leash length recommended for training, walking, hiking, etc. Most dog trainers do not recommend extendable or retractable leashes. When choosing a size, follow the collar guidelines below -- each collar size is matched with the best leash width for dogs of that size.    

Size Leash size Collar fits neck size...
S 5/8" wide and 6 feet long 10-14" (5/8" wide)
M 3/4" wide and 6 feet long 14-20" (3/4" wide)
L 1" wide and 6 feet long 18-26" (1" wide)