Flex is a very strong and flexible material. There are many use cases where hard plastic is not the ideal or even unusable at all. But whether you need a phone cover, an action camera case or wheels for your RC car, flexible is the way to go.
Before you start printing from Flex, clean the nozzle from the previous material - preheat the nozzle and load PLA to remove any other previous material. When loading Flex, loosen the extruder (idler) screw(s). Keep in mind that when printing from Flex, the automatic filament change function may not work properly.
Flex has very good abrasion resistance, remains flexible in cold environments, and is resistant to many solvents. It doesn’t shrink much when cooling down, so you can be fairly accurate with your measurements and perfect fit models.
Flexible and elastic
Needs more steps when loading
Can be tricky to print
Good layer adhesion
Needs to be printed slowly