u/Agreeable-Broccoli46

I marked this as a Metrication-US post because it involves the annoying use of the US customary system.

I was looking to buy a propeller for an RC boat, which is when I found out that, in the US propeller diameter is in metric, while the shaft diameter is in US customary; everywhere else in the world, it is all metric. Since I have an American RC boat, I wound up getting a 1/8 inch shaft diameter, 63 millimeter diameter propeller. That exact same propeller could be found on a non-American website as a 3.2 millimeter shaft diameter, 63 millimeter diameter propeller. One of those is much easier to understand.