Laser center/edge finder I used on my system with a Hypertherm 85 torch. It uses a 9v battery(not included). you will need to solder a connector at the end of the wire to be able to attach a battery to it or you can hard wire it to your system which is how I had it. also the on/off button sometimes sticks, a quick flick of the button and it's fine again. The bore is about 1-5/16".