Installing the handlebar extender so I can mount some phone mounts to it

 

The handlebar extender pieces are all metal and look to be of pretty good quality.
There are a couple different sized internal spacers in the attachment brackets. I didn't use any of them due to the larger size of the RadCity's handlebars.
I wrapped electrical tape around the RadCity's handlebars to create a "custom spacer" to accommodate the handlebar extension attachment brackets.
When tightened down the brackets pieces should be close to flat / aligned with each other so the screws go in easily.
Repeat the process on the other side with electrical tape and tighten it up then slide the extension bar though and tighten in place.
The wires to the bike computer were touching the screws on the handlebar extender so I wrapped them in some split loom to help protect them from any wear.
The handlebar extension installed and ready for some accessories.