This is our brightest MR 11 bulb. It has 18 high-powered led bulbs, which produce about a 3 watt bulb. The light pattern is perfect for illuminating displays or even just adding accent lighting yet it is still bright enough to be used anywhere. LED bulbs are compatible with all types of magnetic transformers but not all electronic transformers. Many electronic transformers require a minimum load which is greater than that provided by LED bulbs. LED bulbs will usually not work properly (no light output, flickering, and strobing) in fixtures that have integral electronic transformers in each fixture. We recommend changing the power LED power supply which can be purchase in our website. In addition, many standard Track Light power supplies will produce voltages as high as 16 with little or no load (LED bulbs provide little load). You must make sure that the voltage of your existing power supply does not exceed 14 Volts with the LED bulbs installed. Product Diameter: 1.375" or 35 mm Product Length: 1.375" or 35 mm