I have been playing squash for several years now and gone through several racquets, a Wilson, a Black Knight, and now a Dunlop. My friend has had a Dunlop racquet for the last few years as well. He has had to replace his grommet strip on several occasions. I believe these damaged grommets to be the reason for his strings breaking. I had a Black Knight racquet for over four years before I broke it on an ill place backhand shot, and in all those years I never had a single grommet break even once. now that I have a Dunlop racquet I am worried that the grommet strip wont stand up as well. if I ever need to replace the string is there only one grommet strip made for a design of racquet or are there tougher grommet strips that I can buy? Or even get a Black Knight one?
Racquet manufacturers (for squash, badminton, tennis, racquetball, etc) these days design specs for every racquet using modeling tools on a computer so that they can get detailed measurements to the manufacturers. The grommets have specs just like the racquets do. The space between the holes in the hoop of the racquet must be known and be precise in order to make grommets that fit properly. Same for the size of the holes drilled in the hoop. So the answer to your question about one grommet strip made for one design of a racquet is yes - grommets are designed/made generally for one racquet only. That's why, for example, on a page like this, they ask which model squash racquet you have when purchasing grommets.
There are some rare cases where the grommets for one type of racquet will "fit" in another if you can manage to heat the grommet (plastic) and stretch it a little so that it fits into the other type of racquet but, like I said, it's fairly rare.
What I would recommend, if you're worried about the durability of the grommets, is find some racquet head tape and put it over the part of the grommets that you're worried will break down (usually from about 9-to-3 o'clock on the racquet head). This will help hold the grommet together and decrease the chance of the grommet breaking and/or splintering - which is the root cause of strings breaking in cases where the string rubs against a sharp edge of a broken grommet. This head (a.k.a "guard") tape will need to be replaced anytime you change the strings in your racquet.
Head tape is an excellent suggestion for the outside frame - just whatever you do don't buy black tape. Many clubs won't let you on court as the black tape marks up the walls. I play with Dunlop and always purchase additional grommet sets with my racquet and have them replaced when restringing. (Often an additional charge if the stringer has to do it as it's a pain in the butt. I always do my own, and only the top.) Grommets on the "inside" of the frame on Dunlop racquets become loose frequently and yes I too feel the strings break prematurely due to the exposed string to the frame.
To answer your question, in my experience, there is no universal or swapping of grommet strips. Unfortunately, purchasing extra strips is the only solution to Dunlop racquets. Well known that Greg Gaultier trims the guard away from the frame and sands the top of his racquets to get even closer to the wall! That's not in my budget.
Now, after Dunlop solves the weak grommets maybe they can develop a consistent ball!!!!