Abstract: A pressure pump delivers a high viscosity fluid (32B) such as grease from a storage can or drum (32A) sealed by a follower plate unit (5) attached to a hollow transfer tube (4). The unit (5) can be air operated to reciprocate up and down relative to the storage can. The unit (5) has a body (6) fitting into the can with fluid guide passage (7) fitted inside a reciprocating cylinder (11) attached by a ring plate (12). An upper plate (17) is attached to the cylinder (11) and a lower plate (16) is attached to body (6) with a ring sealing member (18) interposed between the plates (16,17). An annular pressure chamber (27) between body (6) and cylinder (11) has a compressed air inlet/outlet port (28) to provide the required reciprocating movement. The seal member (18) can act as a bellows to maintain a seal as the cylinder reciprocates vertically.