Although the glass must be accurately-calibrated, industry guidelines only require a pint to be at least 95% liquid, allowing 5% of the pint to consist of the foamy "head". The Campaign for Real Ale (CAMRA) has described this practice as selling a short measure, and says that it costs drinkers £1m a day in beer they have paid for but not received. The British Beer and Pub Association has issued guidelines for bar staff to give a "top up" to any drinker who is unsatisfied with the measure they receive.