Here is one standard impression kit.
It took two weeks from time of ordering it to arrive in the mail. No shipping number or any tracking is arrived. They say it would be 10-15 business days on the website, so you gotta have faith during that time.
3 trays to choose from. Two masses that you mix together. Not too difficult. Two sets of instructions (German/English) and one copy of visual instructions.
It is a somewhat uncomfortable experience to have this tray in your mouth for the time they suggest! Not too bad, but I was happy to take it out. Drooling all over the place wasn’t that much of a surprise.
In case there was anyone hesitant to try this out, I offer my experience. I’d answer questions on the subject; I ordered it from the same place as everyone else (so I believe)
the only negative aspects of this process is the time it takes to wait for the shipping, and then that dread of not knowing 100% whether the impressions are good enough or not.
I don't have the expertise to be able to tell you if that impression is good enough, but at least the split behind your left molar is not in an area where the acrylic will be poured onto the cast to make the expander.
I also used the largest tray when I made my impression even though my intermolar width is just about 34mm and my wisdom teeth have been extracted. I wondered what people with larger arches would do. If I successfully increase my intermolar width and then want to order a second expander, I might not be able to fit in the largest tray to take an updated impression. I suppose I could request an extra large tray or order one from somewhere else, or just go to a dentist to have my cast made.
What are those lines along the palatal impression?
When I did mine I pushed up with my fingers on the tray, forcing it into my palate to create an impression of all the ridges and such. Then, during the 6 minute wait time I pushed it into my palate with my tongue, which ended up making a nice impression of the entire palate. The instructions said to map out the entire palate.