Just for kicks I put a Glock 17 stainless steel guide rod in, and it fit like it was meant to be. Gen 3. Not that it matters, just some info for ya. So I would imagine a Gen 3 19 guide would fit as well, just had the 17 on the nightstand so that's what I tried. I was so amazed at how well it fit I went to Amazon and put a Gen 3 19 stainless with a bit heavier spring on my cart.. Lol