I go through a lot of oil in my shop. In an effort to save a little money and reduce waste, I drain the oil left over from every quart into another container to use later. There's never much left - just a few drops maybe, but over time, this adds up. My dad used to tell me about when he was a kid and road a motorcycle. He never bought oil for his bike. He'd just scavenge oil containers from the garbage bins at gas stations. That always stuck with me.
Rather than re-invent the wheel - or the threads in this case - I used the oil spout model by radare as a basis for my adapter. I cut off the spout, mirrored the threads horizontally then again vertically.
This is designed to couple two quart bottles together. Probably just another of my fringe case models, but... if you need it, here it is.
Due to either a Thingiverse bug or (more likely) shadowbanning, my models no longer show up under the [Newest] listings. If you want to see more of my models, please be sure to 'follow' me. If you print this, it would really help if you'd post a 'make' so that others could find this model.