The internal profiles of each Glock OEM magazine are not all identical. Competitor companies offer “one size fits all” type extensions that create lips and overhangs where the extension and magazine connect. You wouldn’t know this without cutting your magazines in half to see the profiles. This results in mis-feeds because the spring catches on the edges and lips while cycling rounds, ending up in failures. Our magazine extensions have a perfect, flush connection where the extension and magazine meet. Unlike the competitor parts, Milspin Glock extensions WILL NOT cause mis-feeds.