D1 - D1R / D1S HID Bulbs
The biggest design innovation over
previous HID bulbs, is that the D1S and
D1R bulbs are attached directly to a metal
box at the base of the bulb called an igniter.
While there are no noticeable performance advantages over D2 Bulbs, D1S and D1R Bulbs are only disadvantaged by a higher cost of replacement due to the igniter being permanently attached.
In theory, the benefit to attaching the bulb to the ignitor is that this design will allow for a more reliable ignition of the arc-lamp in cold weather where a weak battery may previously have caused spiking and ignition failure.
