I have two extensions made years ago by another guy that was on the Seecamp forum and I believe on this forum.The first one I had a heck of a time getting it to work and stay on the magazine. I hated it until I got it to work. The second one seemed a lot better, both for the .380 model.
I showed my magazine extension to Larry Seecamp, he was never crazy about the idea of an extension.
He also stated that the material, being aluminum just may not be the best choice for a part on the pistol.
I really never thought the magazine extension helped me control the pistol.
And really do not trust the material, maybe one made of stainless steel?