Worked with my existing ballast. No rewiring was needed. Slipped ends into tombstones and turned on the switch. MUCH faster warm up and no cold flicker, black ends or strobing. Replaced ALL of my FT40's and T8's in my workshop (36 tubes). I expect considerable overall savings of electricity usage with a very quick payback. (36 tubes x 40 watts@14 cents KW = 1,440 watts per hour = about $.20 per hour. -OR- 36 tubes @ 8 watts = 288 watts = about 5 cents per hour. Figuring lights are on 10 hours a day you can save $1.50 a day. 30 days results in a $50 savings. Payback comes quick and they are brighter!