Hareline's Hollow Tubing has an outside diameter which is approximately 0.02″ for micro, 0.03″ for midge, and 0.04″ for standard. Same concept as the old skool Midge Lace from Larva Lace but better. The micro is great for the tiniest of tiny flies; the midge is great larger midges, nymphs and stoneflies; the large is great for Crazy Charlies and larger nymphs. Standard is available upon special request. 2 feet per package.