T10, T16 (W10W, W16W). I would suggest LEDs.
Some example, i have something similar:

Paar 1200LM BMW Canbus LED T15 W16W 921 Glühlampe Rückfahrlicht Rücklicht Weiß | eBay

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I have LEDs from these guys. Good product, great service, reasonable cost

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Hello! I was searching around the internet to find out what socket to use for an upgrade for my reverse/back up light. I drive a 2015 v6 tdi and here in sweden it’s really dark nowdays. So I need help to confirm what socket I need? In the picture are the original halogen lamp I pulled out. View attachment 241927

I have leds similar to these which are pretty bright. W16W there are many to choose from!!

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