A set of four large neoprene pump seals / valves for the H4, H5 & H6 range of Lister H water pumps.
See illustration number P6 in the Lister Shallow Well Pumps and Spray Pumps booklet for further details.
The seals are 2,1/2" diameter, 7/16" thick and have a 1/2" hole in the centre.
You may need to relieve the centre hole slightly as they are punch cut in manufacture and tend to leave an "apple core" shape meaning the middle of the centre hole is sometimes slightly smaller than the required 1/2" and requires carefully opening out to suit the exact fit required.