I just purchased an AR ES-1 turntable with a Sumiko MMT arm. Is the protractor sold by Turntable Basics correct for this combo?
Unusually the MMT is a fully paid-up Baerwald design, so the TT Basics protractor should not only work fine but your cartridge should end up nice and square in the headshell and fairly central in the slots once aligned. It's got exactly the same null points as Sumiko intended.
As the other guys suggest you could save a few quid by printing your own from the library, or by using Conrad Hoffman's arc generator, but if you like mirror protractors the TT Basics version is supposed to be a good one.