I always buy holsters made for the gun but can say that I have a leather holster made for a Ruger Security Six which fits both a K and L frame nicely. The Security Six was a little beefier than the K frame. I've also been able to fit a GP100 in this same holster (although it's a tight fit), and the GP100 is beefier than the L frame.

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Ephesians 6 (Armor of God)