I wouldn't know as I don't use them, but what about cutting one of your old ones off and measuring it?
And I wouldn't worry about the material too much as they will hopefully only ever come into contact with water.
Another vote for the castration rings. I've used mine for a number of years now to hold a phantom crab captive at the end of a 8mm dyneema 'sling draw' and they work really well. They're also very robust and long lasting.
In reply to Radioactiveman: actually I prefer o rings to the petzl strings, they are lighter allow the tape to dry quicker and keep the biner more captive. I find the strings split slightly up the sides and loose their gripyness.
> (In reply to Mark Sheridan) how do they fit to the quickdraw? just snugged up to the biner or like an o ring.
yeah, they just snuggle up, all close and friendly like, but because they have such a tight hole (ooooh matron!)they stay put and don't move about at all. They do work best with a more rounded sling (mine are the 8mm Mammut ones).
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