3/8" Tubing - Black (100' coil) is used for a long run between nozzles over 25' due to friction loss in smaller tubing without nozzles.
Is also used to boost pressure mid-length in long straight runs, but normally multiples of 100' is required for that use. Example: 70 nozzle circuit is approximately 700 feet long, thus halfway is 350 feet so it would require 4 of these 100s but it is cheaper to buy a full 500' roll at that point.
THIS IS NOT NORMAL SIZE NOZZLE CIRCUIT TUBING. THIS IS SPECIAL (LARGE) SIZE TUBING FOR OTHER USES.