This is the factory GLOCK 10mm barrel that comes stock in the GLOCK model 20 and 20SF. It can also be used to convert the 20C to shoot as a non-compensated. Using it to convert the 21 or 21SF to shoot 10mm is not recommended and unsafe as it is not a 100% fit. This barrel will not work extended in the 29 or 29SF due to the difference in the locking blocks.
Glock Barrel 10mm 4.6" Black Glock 20 SP05355
WARNING: This product may contain chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.P65Warnings.ca.gov