The design of the base and contact points isn't good either. I put in an 1157 for the brake lamp, and the light was on intermittently. I could jiggle the bulb to get it on, then after you lock it to the fixture, it goes out. the tiny little contacts just don't work right. BTW- the first attempt with the rear turn signals used the SMD type bulbs, and the second with the front turn signals used the traditional LED bulbs. Also, when I tried the latter in the rear brake lamp, it created a 'hot spot' on the lens both with the brake off and even brighter with the brake on. Maybe the SMD-equipped lamps would be more like incandescent bulbs. IMO, To use LEdDs in the tail lamps and any other lamp on the exterior body would involve re-engineering the lamp with an array of LEDs, like Dave (Zs-ondebrain) has done. That is, until you can buy an LED panel that fills the lens with light.