The ZYYX Soft Spring is an accessory for use if you are printing flexible materials suchh as TPU, TPE, NinjaFlex, soft PLA. For more info see this article.
Package of 1 spring and 1 spring removal tool.
As a starting point you should use the predefined ZYYX TPE Material setting in Simplify3D, this will work for most types of flexible filaments. Most important is to print slow and with the correct temperature. Even with the Soft spring if you print too fast or with too low temperature the extruder can still jam and filament can creep out the side.
Before loading a soft filament it is extra important to make sure the extruder is in good condition, a good way is to perform a couple of cleaning cycles with out Extruder Maintenance Kit.