[unwind]

It's awesome that they combine 1" pipe with a 5 mm hex [1] (often "Allen" in the US) fastener. :)

[1]: https://en.wikipedia.org/wiki/Hex_key

[gibspaulding]

You see a lot of this in the bicycle industry. There are a lot of older standards in use like 9/16” pedal threads, 1 1/8” steerer tubes or 1” (25.4mm) handlebars but any new standard is metric - so bottom brackets, wheels, newer seat post diameters are all metric. It can make for some very strange looking spec sheets.

[bluGill]

The actual size is 27mm. If you convert to an imperial system the size is not a nice number.