Both the 0940 and 1045 receivers are designed to accept Glock double stack magazines in their respective calibers. We recommend the use of OEM Glock magazines. While most 3rd party/aftermarket magazines will work, some may cause feeding issues, not latch properly or fail to operate the last round bolt hold open feature. We do not troubleshoot issues caused by 3rd party magazines. If you are having magazine issues please see our Troubleshooting section.