sentences:  Regulation snooker balls (which are specified in metric units) are nominally 52.5 mm (approximately  inches) in diameter, though many sets are actually manufactured at 52.4 mm (about  in).No weight for the balls is specified in the rules, only that the weight of any two balls should not differ by more than 0.5 g. Some recreational sets (which are usually not measured metrically) are  in (about 54 mm) up to as large as pool balls, at  in (about 57.2 mm); larger ball size requires wider pocket openings.Miniature sets also exist, for half-size home tables.