In general most parts on a trampoline are interchangeable between brands e.g. spring padding, however the Jumping mat size needs to be a very close fit or you could easily end up with a mat that's not right.
Too loose = no bounce = no fun
Too tight = overworked springs and mat stitching = shortened trampoline life or an unsafe condition
There are many manufactures and brands in the market place without a structured industry sizing standard, the end result is that the actual frame diameter and spring length do vary a lot which means you simply cannot order a mat based on trampoline size and spring count alone.
We stock 7 different mats for 15ft Trampolines and this still doesn't cover all the variations in the market. We have provided this Mat Size Calculator to help eliminate the guesswork. Please take the time to measure accurately as shown.