ml ). ▁However , ▁as ▁there ▁are ▁ 1 6   US   fl   oz ▁to ▁a ▁US ▁pint ▁and ▁ 2 0   imp   fl   oz ▁per ▁imperial ▁pint , ▁the ▁imperial ▁pint ▁is ▁about ▁ 2 0 % ▁larger . ▁The ▁same ▁is ▁true ▁of ▁qu arts , ▁gall ons , ▁etc . ▁Six ▁US ▁gall ons ▁are ▁a ▁little ▁less ▁than ▁five ▁imperial ▁gall ons . ▁ ▁The ▁A voir du pois ▁system ▁served ▁as ▁the ▁general ▁system ▁of ▁mass ▁and ▁weight . ▁In ▁addition ▁to ▁this ▁there ▁are ▁the ▁T roy ▁and ▁the ▁Ap othe car ies ' ▁systems . ▁T roy ▁weight ▁was ▁custom arily ▁used ▁for ▁pre cious ▁met als , ▁black ▁pow der ▁and ▁gem st ones . ▁The ▁tro y ▁ ounce ▁is ▁the ▁only ▁unit ▁of ▁the ▁system ▁in ▁current ▁use ; ▁it ▁is ▁used ▁for ▁pre cious ▁met als . ▁Although ▁the ▁tro y ▁ ounce ▁is ▁larger ▁than ▁its ▁A voir du pois ▁equivalent , ▁the ▁p ound ▁is ▁smaller . ▁The ▁ob sole te ▁tro y ▁p ound ▁was ▁divided ▁into ▁ 1 2 ▁ oun ces , ▁rather ▁than ▁the ▁ 1 6 ▁ oun ces ▁per ▁p ound ▁of ▁the ▁A voir du pois ▁system . ▁The ▁Ap othe car ies ' ▁system ▁was ▁tradition ally ▁used ▁in ▁ph arm ac ology , ▁but ▁has ▁now ▁been ▁replaced ▁by ▁the ▁metric ▁system ; ▁it ▁shared ▁the ▁same ▁p ound ▁and ▁ ounce ▁as ▁the ▁tro y