A container (1) for releasing a chemical additive (7) in a fluid material selected from a lubricant or hydraulic fluid composition comprises a fluid material-impermeable casing (3) having a hollow interior and an additive composition (7) comprising at least one fluid material-soluble additive. The additive (7) is held within the container (1) by a least one fluid material-permeable element (11) provided at or near an opening (13) in the casing (1) and is effective to provide for release of additive(s) (7) into the fluid material. Methods of releasing additives (7) into fluid material are also provided.