I carry a 640 sometimes in a Kramer holster with plus P's. I forget I have it on , but then again I never carried an airweight. I hate the internal locks and I simply can not believe S&W still keeps insisting on using the ridiculous things. It jeopardizes their dependability and it ruins them aesthetically even with a plug. It ruins their guns as far as I am concerned, which is why I have stuck to a collection of LNIB pre locks. Never owned a IL and never will.