The 8 1/4 thread

Higher number as in above 2.45
Not sure which carrier that is that you have. But that is the "break point". Any ratio from that point and numerical lower takes 1 carrier
Any ratio above that (2.71, 2.94, 3.21, 3.55 and higher yet) takes a different one. Luckily "most"take the same one, not as many 2.26 or 2.45 out there