Abstract: A transfer adapter for connecting a bag or a tubular liner (510) to a container (60) for filling or emptying said bag or a tubular liner. The transfer adapter has an adapter unit (20) for connecting to an aperture of a container, the adapter unit having an inner wall delimiting a transfer opening, and a retaining (101, 102). The retaining unit includes a retaining fixture (11) for receiving a circumferential strip of a bag or of a tubular liner (510), and a retaining element (12) being configured to hold said circumferential strip in the retaining fixture (11). The retaining unit (101, 102) is dimensioned to be removably positioned inside transfer opening such that the transfer opening together with the open bag or together with the open tubular liner (510) form a transfer passage. A transfer system also includes the adapter as well as a method of transferring material between a container and a bag or a tubular liner through the transfer adapter.