best O ring material for holding lights

[Pale Rider]

Thanks everyone - very helpful. Just ordered a couple of EPDM o-rings from Sealforce on e-bay. No, I couldn't use a zip tie, and an o-ring is much neater anyway.

In the absence of any better information I think you are wise to go with the Garmin recommended material.

I've never heard a complaint of a Garmin O-ring mount failing.

You could deploy two if there's space.

It's unlikely they would both fail at the same time, and assuming you spot the first one to go, it would give you early warning of a second failure.