Very neat and effective method of wiring. I just drill a hole 6 mm deep 1.78 mm dia.(This is what a nom 1.8 mm drill measures). I then grip a 1.3 mm drill in a pin vice allowing about 5 mm to protrude, Place the grommet over the drill and push the grommet firmly into the hole. To ensure good contact I give the pin vice a gentle tap with a small hammer.