The Office of Fair Trading says it would expect to see lower prices for smaller drinks, as it consults about the size of Manx measures.
The Isle of Man's standard spirit is larger than in England and Wales but smaller than Scotland's - and it's causing problems as pubs can't use standard optics.
The OFT says it's considering introducing UK measures - which would also help people accurately track how many units they've drunk.
But chief inspector of trading standards John Peet says if measures do shrink, so should prices in pubs:
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