This is the factory GLOCK 9mm barrel that comes stock in the GLOCK model 17L. It can also be used as an extended barrel to convert the 17C to shoot as a non-compensated. Using it to convert the 24 to shoot 9mm is not recommended and unsafe as it is not a 100% fit. This barrel will not work extended in the 19 or 26 due to the difference in the locking blocks. You can use it as an extended barrel in the GLOCK 17 and 34.