Review on 🔦 27mm Festoon Light Bulbs | 1.10" 2835 6SMD | DE3021 DE3022 3528 LED | Xenon White Interior Lights | 12VDC Dome Roof Door Step Light (27mm) by Michael Cox

What I liked about these bulbs is that they are actually 27mm long. Both of my cars have 27mm string lights, but if you use the search for compatible bulbs on any auto parts site, the search always returns 31mm bulbs which will not fit (I've tried). I use them for my car's map lights and my van's trunk/load compartment lights. As you can see from the photos, this is nothing out of the ordinary. The design is very simple: six LED chips on the board, soldered to some end connectors. As far as I can see there is no heatsink or anything on the board. They are sold as indoor lighting and I agree. I would use them for applications that only require short usage times. They're no brighter than the incandescent bulbs they replaced, but the color temperature is different if you like the difference. The plus for me is that they use less energy and don't heat up.