If they can be repaired, for older models, they are springs and padding here they call it wadding, some also have foam.
Thank you very much for stopping by and commenting, I started taking photography with a 28-135 which died and I have not been able to repair it, Later I had a 50 mm that still exists, also a 14 mm that I really like, currently I am using the 24-105.
Maybe soon I'll take some photos with the 100 - 400, I think I have to start in the gym, it weighs crazy. I need a tripod to take moon photography hahaha
Equipment is important but it's not the first thing to worry. You are doing great as it is. After decades of craving for it, I finally have a bag full of prime lenses but I realised that although they are amazing and help me a lot, they haven't change my photography itself at all.
That 100-400 sounds like a beast :)
Cheers!
I agree with his words, in the end one ends up using very little, although if you feel lucky to have the choice, the lighter your luggage is usually the better. Yes, it's really interesting, I haven't used it too much but I hope to do so soon. Thanks for stopping by, cheers