if there is a manufacture sticker on the unit with a model# then you can google it and find out exactly what you have and what bulbs to run in it. As DP said many of todays ballasts are switchable (either manual switch or auto) and can run either bulb type which is really handy easy way to tell magnetic from electronic type ballasts would be weight. the magnetic type weigh a considerable amout to the point of dont drop it on your toes and the electronic are very light in comparison. I'll stay away from tech stats as I dont want to add to the confusion. look for that label and google it :jointsmile: