Just got off the phone with them as I've accumulated some questions of late.
The M600 & M800 older types, on sale are Saint Hubs specific; reduced in price.
The M810 newer, still quite dear as you'd say, fits most anything.
The chap fired-it right-off. I suppose that due to the huge discount, folks've been inquiring. "it can track different types of cog sets" says the ad. and the man.
By all means, have others weigh in, take it all under advisement, as I'd said I'd had another thing to ask him anyway & got lucky with a knowlegeable fellow.