I just bought two aluminum main spring housings for a pair of my Colt Officers from Smith and Alexander. I could not believe how far off all the dimensions were.The tube where the mainspring plunger went would not accept the standard Colt parts. I drilled it out to 5/16" and polished it.That fixed that problem. Then I found the the housing would not fit flush with the botton the the frame, it would when no parts were in it but then the housing pin could not be driven in. Has anyone had this experience with their parts? I wonder if they will stand behind them and will let you know. For $35 each I think they should fit real well.