Ordered a boardman feeder recently. The design is quite straightforward, except for one thing: The round hole is 3/8 of an inch larger than the mouth of the Mason Jar, which allows bees to go into the tiny space around the jar and feed "from the top", rather than the open mouth of the boardman.
Mason jars are standardized, and I don't understand why this is sized in this manner. Ideally, I'd expect the mason jar to fit perfectly into the hole.
Can anyone help me understand?