How to get injector seals on?

So I've removed the injectors and cut the old seals off one. I ordered these green upper injector seals a while back (part number 034133557E) https://www.heritagepartscentre.com/au/034133557e-upper-fuel-injector-seal-k-jetronic.html.

I did the Sharpie trick and lubed up the injector seal and injector and tried to slide it on, but it just wont budge passed the first ridge where the smaller O ring goes.

In fact I tried so hard to push the O ring onto the injector I ended up splitting the and ruining the O ring.

Is there a way to do this?

(Also, maybe my new O rings where old and stiff? They'd been sitting in a plastic bag for about 5 years)

Many thanks in advance

They should by nature of their job be fairly soft and supple, try some oil on the seal and it should roll on. If they have hardened to the point you can't get them on they may not seal in the injector seat well

Agree with Jake, they should go on quite easily. I've never had any issue fitting them. I always think they should be a tighter fit! Probably worth getting some new ones  - https://www.ebay.co.uk/itm/190669091413