Comparison of the imperial and US customary measurement systems adopted a system based on the 231-cubic-inch wine gallon for all fluid purposes. This became the US fluid gallon. Both the imperial and US fluid gallon are divided into 4 quarts, 8 pints or 32 gills. However, whereas the US gill is divided into 4 US fluid ounces, the imperial gill is divided into 5 imperial fluid ounces. So whilst the imperial gallon, quart, pint and gill are about 20% larger than their US fluid measure counterparts, the fluid ounce is about 4% smaller. Note that one avoirdupois ounce of water has an approximate volume of one imperial fluid ounce
Pint glass look-alike could naturally be affixed to the glass, as long as it is done in such a way that it is not confused with the CE marking". Selling beer in unmeasured glasses without using some other form of calibrated measure is illegal. Half-pint, one-third pint and two-thirds pint (schooners) glasses are also available, and are subject to the same laws. 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