Hoses are generally measured from centre to centre of the banjo.
If you're looking for standard length replacements, I'd recommend opting for one of the following: -
Goodridge
Vernhill
Hell
Earl's
All of the above I've fitted over the years, all are good, some are in my opinion are easier to fit, require no assembly, supply all hose fitting rubbers and fit better (Goodridge). Others require various levels of assembly, you've got to supply hose rubbers or P clips and the fit isn't as good. A few dealers and pad suppliers (EBC, TRW, ) now also do a range of hoses, these are ok and are a mix of the above, without some of the nicer finishes.
All of the above will supply bespoke hose lengths in any finish.
I've never used Amazon neither would I. That said doesn't make them bad, it's likely they are a branded supplied hose, just sold by Amazon, in which case they're good. If they are branded Amazon, they'll likely to be low spec i.e. nickel, non coated, in which case you'd do better avoiding unless money is really tight and you don't mine a lesser finish.
