FR-S Monogram Factory HID in Spec D headlights
 

Hi all, so my Fr-S monogram headlights look great but they're starting to yellow and I like the look of the Spec D headlights more so I figured now is a good excuse to upgrade. Does anybody know if you can use the factory HID bulbs and ballast with the Spec D headlight? I don't want to buy aftermarket if I don't have to.

They should work hypothetically, you will need to mount and seal the ballast since it's exposed on the underside, and get the correct adapter or bulb for H1 socket (I believe), stock uses D4s

So the spec d light uses h1 and stock uses d4s? So I can just mount the ballast on the underside of the light, but I'm assuming it doesn't bolt right up so I'd need to secure it with like silicone or something? Also where would I find an adapter to convert d4s to h1?

I would just have your oem headlights sanded and polished. Buy Osram CBi bulbs. This will still be way cheaper than spec D/conversion kit.

I would never go from your rx350 bi xenon projectors to something off brand. Also going from a true D4S bulb to an H1 HID copy is a downgrade imo.

They do make D4S bulbs with just a H1 socket, it's how they're connected. But to answer OPs question, why go through all that work when you can just wet sand it and get it properly recleared