If it's any help, I jammed on mine some that I think come from a Gemini,(maybe Oz equivalent of a Vauxhall Vivas' little sibling/cuz -'70-80's), just about a 2mm or so square section 'O' ring and as I think someone said a while back that they maybe don't do much, except stop any excess running down, as they sit at the top of stem/end of down travel, but I can't see it doing any harm??
Put 'em on a long time ago but as the maggie shat itself soon after, I'm still getting it back up'n running so can let you know later. cheers ,duTch