The first place to start when updating your jetted bathtub is to look at the suction cover. That is the piece in the tub with all the tiny holes in it. There is usually a PN (part number) on this piece. There are not other part numbers on any of the other items in the tub. Nothing on the jet covers (escutcheons) or the air controls. If you can figure out the brand of the suction cover then that will usually be the same brand of Jet Trim and air controls and air button.
you can begin your search on our site by shopping by the brand of your bathtub. We have been able to identify most of the pieces inside each brand of tub shown on our site. www.uspartscenter.com
if you are unable to match up what you have in your bathtub to what is shown online you may email us photos of what you have and we will match them up for you.