Kia/Hyundai part numbers (you get one of each):

17511-16000 (Fill)

45323-3900 (Drain)

I recently changed the dual clutch transmission in my 2018 Kia Niro and bought a pack of 10 of each for the fill and drain crush washers. Figure I would offer the set of two up for cheap so you can save some money.

These work for both Hyindai Ioniq and Kia Niro first gen. After a complete drain, I added two full quarts of Red Line MT-LV, and it did not seep out of the fill hole even though I leveled the car. Capacity states 1.7 quarts, but two quarts max so I left it at 2. It shifts much better even though the old fluid was just a little bit more amber at 85,000 miles.

I highly recommend doing this service. The picture shows the fill washer toward the rear of the vehicle, but there is a second one in the front that is far easier to access.

The set of one drain and one fill washer will ship in a plain envelope.

Torque spec is 50 ft-lbs for both.

https://www.kniro.net/transmission_gear_oil_repair_procedures-1184.html