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It's an older sit-on sink Builder - OCD me doesn't like sit-under sinks, makes me go all woozy thinking about what might lurk 'under the rim'....
It all looks pretty straightforward but I'm just curious why the cone-shaped basin thread seals, basically like a small rubber tyre, aren't mentioned in kitchen sink contexts but always for bathrooms. It's the same technology in question.
I shall probably invest a majestic £1.35 on one, and have it by just in case.