I believe standard but not sure... it should not matter with Diode Dynamic bulbs though. So if you are looking to buy OTHER bulbs, don't waste your $$. I did at first, bought cheap bulbs (from the site mentioned AND another place) and had nothing but issues. Have not had a single problem since switching to the Diode Dynamic bulbs.

 

Confirmed with my test light, these are standard base bulb sockets. The LED bulbs I had used, may have been CK type. Used these and they work perfectly , and did not matter which way they were plugged in:
https://www.amazon.ca/gp/product/B01...?ie=UTF8&psc=1

$16.99 /pair, Canadian shipped!

Too bad we have to use load resistors.Mounted them to metal to help with the heat.

 

When those bulbs die let me know.

I had similar bulbs on my truck for the taillights. They didn't blink just stayed on and I had no idea as no error code was generated nor was there a flash flash. They just stopped working. I didn't know about it till I saw in my rear view next to a wall nothing was BLINKING.

I pulled them out and put the Diode Dynamic ones in

 

Please don't waste your time with cheap LEDs like those. You're just going to end up replacing them.