Limiting conditions and a listing of assumptions are usual conditions of most appraisals. For example, the appraiser cannot guarantee that the wine is good or even drinkable although knowledge or reference books will usually permit the appraiser to comment on the probable drinkability of a particular wine. Storage conditions can make a difference between a bad and good bottle of the same vintage. And even if the wine has been properly stored, bottle-to-bottle variation is normal. Short of an assessment by tasting, the appraiser can only provide comparisons to wines of the same bottle size, vintage (year), and maker.