Some vinyl tubing is measured ID and some OD so that may throw you off. I have seen 2 different size bleeders but either 1/8" or 1/4" ID should work. Fuel line hose is measured by ID so you can use that if need be. I like to use surgical tubing as it stretches over the bleeder and stays there if clean (clean the ends with brake cleaner if it gets slippery from the brake fluid and it will stick nice again on the next bleeder) and gives you an extra hand and will flex down into a coffee can or drain pan better.