So, I'm looking for 11mm (7/16th) ID grommets (it's for pressure washer tool storage) so I'm trying to find then on Amazon and FleaBay. And this caught my eye:
"Package Includes:
20 Pcs - 14 mm
20 Pcs - 17 mm
50 Pcs - 11 mm
20 Pcs - 15 mm
50 Pcs - 10 mm
50 Pcs - 9 mm
50 Pcs - 8 mm
Warm Tips: Due to different measurement methods, there is a deviation of 1-2 cm."
So ... there can be a 2 cm error in measuring or manufacturing a 8mm part? Okay ...