The white Tramadol imprint 355 U has a coating ( easier to swallow and easier to digest) butit does work for me for it doesn’t digest in my stomach so no benifet for me. I have found a manufacturer Uni Pharmaceutical, they make a yellow pill, imprint 018 , it either doesn’t have a coating or a slight one.
https://www.drugs.com/answers/tramadol-manufacturers-work-best-3558180.html

