This is the factory GLOCK .40 barrel that comes stock in the GLOCK model 22. It can also be used to convert the 22C to shoot as a non-compensated. Converting the 31 or 31C to shoot .40 s&w is also possible. Using it to convert the 17 to shoot .40 s&w is not safe as it will not fit into the slide properly. Calibers can only be converted down, not up. This barrel will not work extended in the 23 or 32 due to the difference in the locking blocks.