Flat burr
A burr set with two flat, ring-shaped burrs that face each other, common in larger espresso grinders.
Flat burrs tend to produce a more uniform particle size, which some people prefer for clarity in espresso. They are often larger, pricier and a little noisier.
The differences are real but subtle, and matter most to people chasing the last few percent of espresso quality.
Why it matters for small spaces
Flat-burr grinders are usually bigger, so a small kitchen may favour a good conical grinder instead.