This is a union to allow 2 oil containers to be connected to allow the remaining oil in the top container to drip into the bottom container. Great for collecting the remaining oil in each bottle after an oil change. I was supprised to see how much oil remained in a bottle after it looked empty. My airplane uses 6 Qts and I normally can collect 1" of oil from the remaining 5 bottle after letting them each sit for 24 hours.

Note, make sure that the side with the straw is connected to the collection bottle (Bottom). I have not seen any issues with dedgregation using PLA+ for the device.