Fole (m)
(with) definite article: oair reservoir: flexible (usually of animal skin), ready for the insertion of stocks
NB: ➺ homonyms, &c.
Traditionally made of kid, goat, or sheep-skin, nowadays [i.e. late 20th century; ws] more generally of rubber (caoutchouc), usually with a simple monochrome (sometimes a patterned) cloth cover.