The auger flight is crucial if you want perfect soft serve. The auger flight scrapes frozen product off of the walls of the freezing cylinder and mixes the product at the same time. The manufacturer recommends that this piece is replaced every six months or until the flight has reached the designated wear line. Fits Stoelting Models: 217, 0111, 0231, 0411, 0431, 0431-RC, 238R, E111, E131, E131-YG, F131, F131-YG, F144, F231, F431, SF144-I2, SU444-I2, U421, U431-I2, and U444 Machines