I have a 30 year old Tefal aluminium 6 litre pressure cooker which has never had a new seal!! Just lately and unsurprisingly it has been getting more and more difficult to make it steam tight, requiring ever increasing turns of the screw. This seal does the job albeit after trimming down. I prised out the old one with a small screwdriver. However, on reflection I suspect the machined holes in the top of the lid are there to poke something through to make this easier.
The new seal just feeds in and hey presto.....new lease of life.
Recommended and a five minute job at the most.