These lamps have two different styles of layout, the loops or tubes can be arranged in a triangle or in a row
The wattages are not interchangable and you cannot fit the wrong lamp in the lamp holder
Again colour tone is important, you need to make sure you match your existing lamps
They come with either two or four pins. The four pins allow dimming and are used as emergency lighting so if your fitting is also an emergency then the chances are you have a four pin lamp in it. Of course the easiest way to be sure is to take the lamp out and check!