that was on my old bike, so quite some time ago, We use 2 part plastic glues at work, so just mixed some up and pressed them together, before it was totally dry trimmed any that oozed into the throttle tube with a fine box cutter knife, then left to dry before refitting
I did like the look of them but they are not much use as heated grips....lukewarm at best. The glue still held when I sold the bike 2 years later. I ended up cutting the wires and kept the controller as I had some Oxford grips I was given with no controller so I used the controller with those on the Valk... works a treat and toasty warm hands
