Ruger SR9C/SR40C Magazine Adapter is a grip extension for the 15 or 17 round magazines. The magazines extend past the bottom of the handgun grip. This adaptor slides on the extended magazine and helps level it out with the handgun grip so that the magazine does not catch on anything when drawing from the holster. The Ruger SR9C/SR40C Magazine Adapter is a factory made piece and should therefore fit your factory extended magazine like a glove. Factory original products are made to all the same specifications and should work together perfectly.