My headlamp brackets fit between my upper and lower triple. To ensure fit and minimize vibration, an X-ring is installed between the bracket, both at the top and bottom. I've been using Buna-N o-rings but they have really, really poor UV resistance and, after about 6 months, crack and fail.
McMaster lists X-rings in a Viton® fluoroelastomer. This is a DuPont product and looking at their website, might have better UV performance. But at $3 each, I thought I'd ask you all to see if anyone had experience with UV resistant x-rings or square o-rings?
