Don't mind me. I'm just amalgamating some knowledge from other threads and UKC to make it a bit more searchable.
If you have an Evo stick (green head and clamp closure) and one of the clamps is slack you can fix it like so.
Remove the grommet from the affected clamp as in this video:
Cut a little square off an old credit card, the same size or just slightly smaller than the grommet. Pop this where the grommet was, replace the grommet on top, and reassemble the clamp.