From Robert Gilmour
Feedback’s jocular mention of a 10,000-millimetre waterproof rating for hiking gaiters (13 April) is actually a hydrostatic head rating. This means that if you were to have a column of water 10 metres tall pressed down on the fabric, the water could not force its way through.
So there’s no need for you to hike through a lake to check they work!
Edinburgh, UK
