I need to refurbish my synthetic drone reeds.
Kinnaird: Great success with refurbishing. Contact the company for new carbon fiber tongues. They make a world of difference. O-rings are 9mm ID with a 3mm wall. (Sometimes called 9mm ID, 15mm OD, 3mm thick.) The allen wrench seems to be 2.5 mm.
Omegas: The only thing I've ever done is replace the allen wrench with a 1.5 mm size.
Crozier Fiberglass: The o-rings are 8mm ID with a 2.5mm wall. (Sometimes called 8mm ID, 13mm OD, 2.5mm thick.)
Shepherd: I have experience only with the black and white originals. The polystrene tongues would fail constantly. These are commercially available. Polystyrene is well known to suffer stress cracking. I bought sheet polystyrene from a hobby shop and made my own.
Ross Cane reeds: The tongues were readily replaceable, but I stopped trying after a while when the little rubber bands gave out. Probably could replace with o-rings, but I haven't done it.
Ezeedrone: no refurbishing attempted (I've worn out the tongues on a couple sets, but just replaced the whole set.)
Best Tone (Caldwell): no refurbishing attempted
David Naill Carbon Fibre: no refurbishing attempted