A filter element comprises a cover plate (5) having an aperture (7), a filter media (6, 30) connected to the cover plate, and an adaptor (8) detachably coupled to the cover plate and located within the aperture. The adaptor has a threaded internal cylindrical surface (12). The filter element further has a coupling arrangement (10) for detachably coupling the adaptor to the cover plate, the adaptor being configured to engage with the cover plate by means of the coupling arrangement such that there is substantially no relative movement between the cover plate and the adaptor when the cover plate and adaptor are engaged. The cover plate is connected to a canister (4) which houses the filter media. The adaptor can engage with a spigot (3) of a filter head by means of the internal thread so that and rotation of the canister and therefore the cover plate and adaptor causes the cover plate with the adaptor to translate along the spigot to bring the cover plate into connection with the filter head. A seal (32) provided on the cover plate provides a seal between the cover plate and the filter head. The cover plate can be detached from the adaptor that can remain in place on the spigot to allow for replacement of the filter media.