The 42" brake line is for the Honda Grom dual-fitting (single caliper - junction valve) handbrake kits.
If you have a Honda Grom with a dual caliper bracket and a second caliper, you will need the 65” brake line. That handbrake line is located here:
Regarding sport bikes, you will need a 56" brake line, which is used for single caliper (dual-fitting) handbrake kits for street bikes.
If you have a dual caliper setup on a street bike, you'll need the 80" brake line.