Bracket used to mount a 2 1/2 pound fire extinguisher to a 1 1/2 rollbar. I used three of these with the standard quick release bracket that came with the fire extinguisher. Each bracket requires four M5 cap bolts and nyloc nuts.
Be sure to use a material which is going to be strong enough. I used Formlabs Tough because it won't shatter if it is overloaded.
More details here.