1156 1156 BA15D 4 Watt LED Bulb. Works negative ground no polarity for both the BA15S 1156 or BA15D 1142. The BAY15D works only negative ground. Up to 250 Lumen output for taillight and up to 300 Lumen output for brake light or a single filament bulb. The BA15S 1156 and BA15D 1142 bulb is a single filament, the BAY15D 1157 bulb is a dual filament. Comparable to a 35 watt incandescent automotive bulb. Vibration proof, glass lens, just like a normal bulb, but it is long life CREE 4 watt led chip. Up to 400 Lumen output. 12.8 VDC @ .224 Amps = 2.56 watts. Not Dimmable. A very nice "old fashion" looking bulb perfect for those who want to switch to LEDs but like the "old fashion" look. 120 Degree viewing angle. Rohs listed. CE certified. Long life up to 30,000 hours. Comparable to 35 to 45 watt incandescent bulb. The BA15D base works by applying voltage to the two contacts on the bottom. For a BA15D base the bayonets are even, the base is 15mm diameter and has two contacts for a single filament. For BA15S base the bayonets are even, the base is 15mm diameter and has a single contact on the bottom. The BAY15D has offset bayonets, the base is 15mm diameter and has two contacts on the bottom.