Most coffee tampers have a flat tamping surface. This is standard for a coffee tamper, and it's the standard coffee tamper used by most baristas - except in competition! Therefore, most of the coffee tampers that we carry are flat. Some baristas prefer a convex surface on their coffee tamper, because they believe that if the tamp leaves a (slightly) concave surface on the coffee in the portafilter, that the extraction will be better, both because the water will be less likely to go around the puck, and because the extraction will be more "uniform." So many baristas use convex-surfaced coffee tampers.
This coffee tamper, called "Fat Man," has a convex tamping surface (see inset photo) to make the coffee bed very slightly concave after tamping. Many feel that this gives a superior extraction. In addition to its convex tamping surface, this is a heavyweight stainless steel coffee tamper (Fat Man) with a high-gloss black finish on its handle. The handle of this coffee tamper is topped with a satin-steel cap that matches the satin-steel base. While the bottom surface of the coffee tamper base is convex, by contrast, the top surface of the coffee tamper base is flat. The elegant black handle connects neatly to the top flat surface of the base. This coffee tamper feels good in the hands, and is an elegant addition to your coffee bar.
Most standard espresso machines (semiautomatic and automatic) use 57 mm or 58 mm coffee tampers. Many people want coffee tampers that fit snugly into their portafilters, and some people prefer a millimeter (or so) of wiggle room within the portafilter basket, so that they can more easily manipulate the coffee tamper while tamping. But note that coffee tampers don't get pushed down into the bottom of the filter basket (which can be slightly tapered) when you're tamping, because the basket is full of coffee. That's why you're tamping it!
So when sizing the diameter for a coffee tamper, it's the inner diameter at the top of the filter basket that you'll need to measure to size your coffee tamper correctly. At The Coffee Brewers, we tend to believe in a firmer fit in coffee tampers (i.e., 58 mm) to minimize loose particles in the portafilter basket. Our "Fat Man" coffee tamper will give you this - beautifully.
You should read our article on "How to Use a Coffee Tamper Correctly for Uniform Extractions" if you're not exactly sure how to use coffee tampers. Note that "How to Use a Coffee Tamper Correctly for Uniform Extractions" was written with the professional barista in mind, so there are various moves described that sound complicated, but these have more to do with not touching the coffee directly with your hands than with pure function. Using coffee tampers correctly is not complicated. The Fat Man coffee tamper gives you lots of weight to work with (no pun intended). Fat Man is a solid coffee tamper, and they're great coffee tampers to use. Fat Man feels good in the hands.
We recommend that you do not wash coffee tampers in the dishwasher, because over time, the dishwasher will damage their beautiful glossy finishes. To clean coffee tampers correctly, simply wipe them down with a damp cloth. You wouldn't want to damage the gloss on these coffee tampers. Your coffee tamper should not be "dirty" in the first place. So don't "wash" your coffee tampers - the Fat Man coffee tamper will be much happier that way!