Sir, – Con O'Rourke (Letters, June 27th) believes that most sectors of the Irish economy and our educational system have now converted to metric units. If Mr O'Rourke would like to join me for a 12oz americano in the cafe in the new science block in UCD we can review evidence to the contrary, or if he prefers, we could do so over a pint. – Yours, etc, GARRETT O'CARROLL Dundrum, Dublin 16.