The type of linear fluorescent lamp you have all depends on when your fixtures were upgraded. T12 fluorescent fixtures are slowly phasing out due their low efficiency, in comparison to T5 and T8 LED tubes. If they were installed in the last 15 years, it is safe to assume that you probably have either a T5 or T8 linear fixture.
Fluorescent tubes come in various diameters and lengths. However, 4-ft T5, T8, and T12 are going to be your most common type.
Since T5 lamps are the most efficient fluorescent tubes and are available at higher wattages, they have been adopted to replace the ever-aging metal halide or high pressure sodium gas lamps. These are generally found in places like workshops, hangars, retail spaces, warehouse spaces, and auto body shops.
If you already purchased a new light fixture, and are ready for installation, check out: T5 Fluorescent LED Tube Replacement
You will traditionally find T8 fluorescent in retail spaces, commercial offices, hospitals, schools, hotels, and nursing homes.
Already purchased a new light fixture? Ready for installation? Check out: T8 Fluorescent LED Tube Replacement
As far as the aging T12 fixtures goes, they are normally found across commercial, retail and institutional businesses.
Ready for installation? Check out: T12 Fluorescent Tube Replacement
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