The O-rings are used to seals the touchdown tube at the back of the barrel on both the Touchdown, Snorkel, and PFM models of Sheaffer pens. It is recommended that when replacing a sac both this o-ring and the point seal should also be replaced.
There are 2 sizes: Standard (Touchdown TM and Snorkel) and Large (1949 Touchdown, PFM, and Tuckaways)
There are 2 sizes: Standard (Touchdown TM and Snorkel) and Large (1949 Touchdown, PFM, and Tuckaways)