7000 miles and for the last 1000 the drive was snatchy like chain slack/ fueling etc.

I have taken the cush drives out and the look pretty sorry, the little rubber connecting the pairs have disappeared into dust on two of them.

So my question is, do I add the inner tube mod to these worn out ones or can I do it to new ones? Obviously the latter is preferred.

thanks Kev and anybody else who cares to comment