The 5" funnel is the ideal size for beer bottles, wine bottles, 1/2 gallon jugs, and 1 gallon jugs.
Without it I always spill stuff when preparing a starter. Now that I have it, preparing a starter is hassle free.
One time I spilled some yeast when making a starter. I ordered this the next day and that's no longer an issue.
I use this for brewing and making cider. Perfect fit for 1 gallon and 1/2 gallon jugs. Solid feel, balances nicely. Buy 2; great for tea and coffee around the kitchen!
When making a yeast stater the funnel is perfect for pouring in the dry malt extract, so it doesn't stick to the sides or spill out. Its also good for pouring in a completed yeast starter into a better bottle.
This is a good funnel for yeast starters when using a flask. While you can us eit with carboys, I'd suggest a bigger one.